Ask Pinkbike: eMTB Sag, Stem Length vs. Reach, Fork Noises, & Saddle Comfort

Jul 23, 2021
by Matt Beer  

Here at Pinkbike, we get inundated with all kinds of questions, ranging from the basic "Can I have stickers?" to more in-depth, soul-searching types of queries like if you should pop the question or what to name your first child. Ask Pinkbike is an occasional column where we'll be hand-picking and answering questions that have been keeping readers up at night, although we'll likely steer clear of those last two and keep it more tech-oriented.





Do eMTBs require firmer suspension?

Question: @JudyYellow asks: "A co-worker and I were discussing eBikes, suspension spring rates, and how that affects the sag rate and an interesting question came up. Should you over spring an e-bike to accommodate for the extra weight of the bike?
Normally to achieve the correct sag rate you would shoot for approx 30% of shock stroke. Sag is mostly determined by rider weight and to set sag you jump on the bike cycle the suspension to charge the spring, add/remove air to achieve ~30% of stroke (on a shock). Go ride....

Bike weight is not usually factored into the sag rate. However... when riding an e-bike you have approx 10lbs or more of extra bike weight which should affect the suspension when landing jumps, drops etc since the shock spring has to soak up the system weight (bike + rider). Is it only the rider's weight affecting the shock spring when landing drops, etc? This is the missing piece I don't have...If total system weight (bike + rider) affects the shock should I go for a 25% sag rate instead? 20%? Same applies for coil springs as well.... Do you go 50lbs up on your coil shock spring if using an e-bike?


bigquotesRegardless of the bike's weight, I would still aim to start by setting up the rear shock with 30% sag (the percentage of the shock stroke used by the system: rider + bike weight, on level ground). Don't forget to include your rider gear in the setup equation.

When manufacturers set out to build eMTBs, the higher forces are taken into account and the kinematics are tuned to accommodate. The weight of these bikes changes the rider-to-machine ratio that mountain bikers are more accustom to, which is why you may see more opinions from motorsport suspension gurus weighing in on the topic.

The important thing to keep in mind here is the front and rear balance of the suspension. Most fork manufacturers suggest 15-20% sag. These sag percentages are just guidelines and can be altered, depending on how you prefer the bike to handle. Don't be afraid to play with these numbers, although it's always good practice to keep notes on what changes you make, in case you want to go back to the original settings. In many cases, you'll end up running more air pressure in your fork than you would on a non-motorized bike - 10-20 psi more, depending on the fork. That's due to the additional loads that end up being put on the bike's front end - like you mentioned, you now have additional bike mass along with your own pushing down on that fork.

eMTBs can undergo some large forces, but setting up the suspension is still all about front to rear balance and tuning the bottom out control.





Can you use a longer stem to increase reach?

Question: @fire-munki asks: "Not sure if this is bike fit or bike modifications! Currently I’m on a 2016 Cube Stereo 140 (18") which is a fun enough bike but over the years I’ve found myself getting less enamoured with playing in the woods doing the same run each time (mainly since I’m to scared to ever really jump/hit drops) so have started heading out further on things closer to XC jaunts.

In an effort to make the bike a bit more suitable I’ve got a newer Fox Float with working lockout, got the stem right on the admittedly tall top cap and lower than stock rise bars. Now looking to make it feel less cramped so looking for longer stems (stock 45mm 0 degree), the great ebay has a few options at 50mm and 60mn 0-degree options. What I’m worried about is wrecking the handling with such changes, my saddle is pushed fairly forward to work on keeping the front down when climbing.

Any opinions either way? The 50mm is pretty much like stock so can’t see it changing it much but the 60mm might be too much? Or just what I need!"


bigquotesThe 2016 Cube Stereo 140, size 18", has a reach of 428mm, which is quite short compared to a typical size large these days.

Changing the stem for something longer will increase the effective reach, essentially, the horizontal distance from your feet to your hands, but it is usually a band-aid fix for riding the incorrect size of bike. You will also notice the slower handling while turning the bike.

Since climbing is a main objective of yours and a stem is a relatively inexpensive and non-labour intensive component to swap out, I suggest giving that 60mm or 65mm stem a try. It will help keep that front wheel on the ground while charging uphill and give you a bit more room in a seated position.


Charles Murray broke onto the EWS scene last year with a sixth place. At 183cm tall, his size medium frame and 65mm stem was an uncharacteristic choice, but didn't slow him down.





Trouble with a new fork spring install

Question: @dirtflipper asks: "I installed a new Marzocchi Bomber Z1 Coil. Before installation, I changed the stroke length from 170mm to 150mm. Everything works great with the shock except two things. One, the shock makes a creaking noise as it moves through its stroke. Two, when the shock compresses/extends ever so slightly it seems like there is a couple mm of play in it. So, if you go over a bunch of very small rocks, the shock does this weird chattering thing as it moves quickly in what seems to be an undamped few mm of stroke. Are either of these normal for a coil? I have never had one before, so I do not know."

bigquotesCreaky noises from bikes can be a nuisance to chase down. If you are confident that the noise is coming from the front of the bike, disassemble the head set and make sure all the surfaces are clean, re-greased, and that the bearings are running smoothly. Any metal on metal interface with dust or dirt between them is suspect; sometimes the crown race on the steer tube, frayed cable housing, or the handlebar/stem interface can be the cause.

As pointed out, the Bomber Z1 is a coil fork. During the recent work to alter the stroke length, the spring preload would have been unwound all the way to add a spacer and reduce the travel. Without any preload on the spring, there can be a few millimetres of movements even without any force applied. By turning the preload dial on the rider's left of the crown clockwise, you will start to preload the spring. There should not be any movement as you described. Once the coil has contact with the preloader, you can tune the spring rate slightly to your preferred sag.

Double check that the front and rear sag is balanced in the 15-20% and 30% region, respectively. Note that preloading the spring too much will make for a harsh ride. If you require less sag and have turned the preloaded more than two full turns from the first engagement with the spring, you may need to go up a spring rate.

Marzocchi Z1 Coil
Coil springs are a popular choice for their small bump sensitivity and linear nature, but they can rattle inside the stanchion if they are not preloaded enough. Over-preloading them can causing the spring to bind and bend out of shape as well.





Getting comfortable in the saddle
Question: @witterisms asks: "I got a new bike at the end of last year (YT Capra), and now the evenings are much longer, I've been able to spend more time on the bike/in the saddle - but increasingly hitting the 2-3 hour ride mark it start to get sore when I am in the saddle, and then sore the day after. As far as I can tell I have the saddle in the best position possible, and the body position is comfortable when riding.

What's best to invest in? Better padded shorts (quick look on CRC shows £30+ for seemingly good shorts) or new saddle - I have seen a lot of Enduro riders on Fabric saddles, they seem to start at £45, but obviously more on the market.

From what I know, its hard to test either. All help appreciated. "


bigquotesIt is fair to say that MTB fit is less developed than in the road cycling world. We move around a lot more on a mountain bike due to the terrain we cover, but that doesn't mean you shouldn't be comfortable.

Chamois shorts are designed to promote blood flow and reduce pressure on the sensitive nerves down there, however, that won't eliminate the problems caused by an incorrect saddle position. Generally, the more you pay for these shorts, the better quality the foam and lycra materials will be. And, what is the price of comfort?

A quality saddle that has been researched to support your sit bones is also part of this puzzle. Specialized, SQ Labs, and Ergon are some of the brands that come to mind as leaders in this game. Retül is a brand designed to find the perfect fit using digital equipment. Their devices can measure your sit bone width and suggest a saddle based on your riding requirements and usually offer a demo saddle program too.

Let's get into some fit talk. Assuming that you are on the frame size that the manufacturer recommends, start by finding your max saddle height. Your knees should have a slight bend when your feet reach the 6 o'clock position of the pedal stroke. If you feel like your are stretching or reaching for the bottom of the pedal stroke, the saddle is too high. If it's is too low, your quad muscles will quickly tire and you could feel some knee pain.

The saddle angle is also critical. A level saddle is the best place to start, but if your handlebars are lower than your max saddle height, tilting the nose slightly lower than the back of the saddle can help reduce any pressure points. You'd be surprised how comfortable this can be. It might feel more like a perch rather than a seat. Keep in mind that your sit bones should be on the widest part of the saddle.

I would even go as far as seeing a physiotherapist that specializes in bike fits if you are still struggling to find that perfect position.

Saddle style, width, height, and angle are all factors in finding the most comfortable position. There are a lot of factors in play here.



62 Comments

  • 16 0
 Preload doesn’t change spring rate, right? It just changes where in the spring your starting point is. Which I guess changes your starting spring rate, but not the actual spring rate.
  • 1 0
 Related question: by cranking down the preload too much past it just touching the coil, would that decrease your available travel? Or are the z1 coils long enough to deal with that?
  • 14 1
 It does not. Preload should be at an absolute minimum, and sag should be adjusted via spring changes, per vorsprung.
  • 1 0
 @emarquar: that’s what I thought. I keep hoping that spindex will make a coil fork conversion to avoid getting multiple springs
  • 3 0
 The springrate only changes, if you change the spring it self. The additional force required to push a spring through its travel doesn't change. What ut actually changes is, that it wont react on small forces as much since the spring already has a preloaded force. So aslong as you don't exceed that preload force your spring wont do much.
Just as an example: you have a spring with a springrate of 5 N/mm. Now you preload it with 50 N, so it already sits 10 mm in its travel. Now the force to actually deform the spring (elastic torsional deformation) any further has to exceed those 50 N. Otherwise it's more like a rigid fork at this point.
  • 2 0
 @Phipu: Yup. It just introduces harshness and potentially a loud top out noise.
  • 1 0
 Preload doesn't alter spring rate, but does increase the force to start moving the spring, which would also mean it requires more force to bottom out the spring. Think of spring rate as a linear line with distance (or stroke) on the x axis and force on the y axis. A higher spring rate steepens the angle of that line (more force required to compress the spring each inch). Preload shifts the x axis such that at full extension there is some force already applied to the spring.
  • 8 0
 Spring rate is a constant... there is no 'starting spring rate' vs 'actual spring rate'.

A spring with 2" of travel and a 400lb rating requires 400lbs to compress those 2", always. But, where you are in that 2" of travel determines how much weight is being supported by the spring. So, on this 2" stroke 400lb spring, 20lbs will compress the spring 1/10th of an inch, 40lbs will compress it 1/5th of an inch, 60lbs will compress it 3/10th, etc. So, when you dial in the preload ring 1/10th of an inch, you're literally "pre-loading" the spring with the equivalent of 20lbs of force to create a support platform to set your sag for positive/negative suspension travel... but that's completely independent of spring rate and every 1/10th of inch of travel still requires an additional 20lbs.
  • 7 1
 A real game changer in terms of saddle soreness for me was the use of chamois creme (it's actually applied to the skin, not the chamois). I tried petroleum based products before, but these actually made it worse. I'm using Assos chamois creme, but there are many comparable products out there. Their skin repair creme is deluxe too.
  • 1 0
 Try Noxzema... works as well as any chamois cream I've ever used and costs a fraction as much.
  • 1 0
 also zinc-based diaper rash cream is cheap and effective
  • 2 0
 Love me some Bag Balm. It's made for milking cows. But it's great for the taint.
  • 5 0
 The easy answer for the eMTB sag question is that bike weight is always a factor in setting sag. Everything unsprung is a factor. Adding weight to either the rider or to the (unsprung parts of the) bike is going to require the same adjustment for sag.
  • 2 0
 This, except I assume you meant "everything SPRUNG is a factor". The unsprung mass, by definition, does not compress the suspension.
  • 1 0
 @barp: haha, yes, everything _sprung_. Not sure how I swapped both instances. At least I was consistently backwards
  • 4 0
 What I've found with saddles is that width is the most important measurement, your starting point needs to be finding your sit bone width so that the saddle supports that fitting properly, then height, then position on the rails, then tilt...the later two become pretty obvious once the first two are sussed out. I've tried plenty of saddles and have a few brands I like, however I did do the full "free" fitting thing with SQ Labs about five years ago and have never looked back....I never get sore, even on the first ride of the year, I attribute that to getting the right width saddle.
  • 1 0
 ^^ This. With the right saddle you can ditch the chamois.
  • 1 0
 Yep, sit bone width vs. saddle width is super important, and it's kind of surprising more wasn't made of it in the article. When my wife was getting into riding, discomfort from her saddle was the main thing that was putting her off. She tried a few different types and with some different covers on to help, but it wasn't until we got the sit bone measurements right and found a saddle that suited that that she was able to find a comfortable setup.
It was broadly similar for me too. On Ergon's saddle width chart I'm right on the borderline between S/M and M/L, and using saddles that wound up being around the size for the S/M saddles wasn't super comfortable for me after a few hours riding, whereas the M/L sizes were primo. Beyond that it was finding the smallest width I could get away with (purely for clearance reasons). It turns out for me that was the SDG Belair 3.0, but that was only after I'd tried a few others. It's definitely worth experimenting with, but mainly once you've got a rough idea of what width to aim for.
  • 2 0
 @CleanZine: Me too...I thought the author missed communicating how important width is, everything else comes from that.
  • 4 0
 @pinkbike - i assume this is a good place for new questions? I have a Thomson dropper post that's frozen into a steel hardtail. How can I get that out without destroying the post? Am I doomed?
  • 2 0
 try some release spray
  • 3 25
flag neimbc (Jul 23, 2021 at 10:13) (Below Threshold)
 Why didn't you grease it up a bit when you put it in? This shouldn't happen. Yes you are doomed. If it's that bad a few drops of 50/50 solution of Automatic Trans Fluid and nail poilsh should unbind it.
  • 1 0
 Pretty much screwed...
I had this happen to my Knolly.

I tried everything and it wouldn't move.

Luckily it had a Di2 port near the BB. I was able tap (smack) it out with a piece of copper pipe.

Obviously this destroyed the dropper post but I saved the frame.
  • 4 0
 I'd try some heat.
  • 3 0
 I would like to piggy back off this....Thomson post frozen in a carbon frame (and I greased it up with lube made for carbon frames..thanks for nothing). Tried heat, tried release spray (sitting for 24-48 hours), tried force, shop wants nothing to do with it. I've come to terms with the fact my post and frame are now one (though its luckily at the correct height).
  • 9 1
 Coke, coke has an amazing ability of eating the corrosion between aluminum and steel.
Pull the bb, try to pour some Coke down the seat tube, let it sit like that for a couple days. You should see some weeping on the seatpost to let you know it’s worked it’s magic.

Used this truck lots on seized spark plugs in aluminium heads.
  • 1 0
 Thanks for the input - to follow up, I've soaked it in penetrating oil, PB Blaster, and something called Aero Kroil that some old-timer recommended. I've tried putting in a vice and trying to twist it with the saddle, but I feel like I'm wrenching as hard as a can without breaking it. I haven't tried heat because I'm worried that'll melt all the non-metal bits in there. I feel like whatever I try next is just going to ruin it anyway. My shop also wouldn't touch it. I think I'm doomed.
  • 1 0
 I would try a penetrating catalyst like PB Blaster. I would spray the interface a few times over 24 hours and let it sit. With normal seat posts, you can put the seat clamp in a vise and use the frame as a lever. Instead of doing that here, I would use a strap wrench to break it free.
  • 3 0
 I do appreciate the advice - I haven't tried the coke trick but why not? A strap wrench wouldn't do it. And @niembc - thank you captain hindsight!
  • 2 2
 @onawalk: coke for the win, multifunctional yet slightly unhealthy product
  • 2 0
 @DanielP07: Not sure how punching the clown is relative here...?
  • 4 0
 take the crank and BB out then flip the bike over so the seat tube is upside down, fill the seat tube with PB blaster and let it sit for a few days. If that fails you will need to cut off the top of the post leaving an inch or two sticking out, remove the post internals and then use a hacksaw blade to cut the remaining bit inside the frame vertically into a couple pieces you can pry out
  • 2 0
 @gtill9000: I certainly meant no disrespect - Honestly, try the home made mix as I said - it will penetrate and eat up the nastiest of binds. It's used by mechanics on decade old rusted parts and such - It's worth a try.
  • 2 0
 @chize: Yes, this is the last-resort answer and it will work. I've done this with steel frames and carbon. Using just the hacksaw blade to cut the post stub will be time consuming and you'll probably get frustrated, but don't give up. Let it sit, get a beer, come back later. Having done this a couple times long ago, I put LOTS of grease on my posts now.
  • 2 0
 @gtill9000: I've had success breaking apart stubborn steel and aluminum parts with creative application of an impact wrench. For example, when I was trying to take the aluminum stem out of the steel steer tube on my 1970s road bike I bought a sacrificial socket, cut a notch in it so it slipped over the perpendicular part of the stem, and in half a minute the torque wrench accomplished what weeks of manual and chemical efforts failed to do. My stem was not damaged in the process but I don't know whether that will be possible with your post. You might end up having to drill holes through a socket and the post, connecting them with a pin or bolt to make this approach with. The post would still be destroyed but it's faster and easier than the hack saw method and safer for your frame. It's not necessarily safer for your person, so wear appropriate protective gear in case the modified socket shatters.
  • 1 0
 *to make this approach work
  • 2 0
 @neimbc: nail polish REMOVER.
And really, if you're out buying ATF, you might as well pick up straight acetone for the mix.
  • 2 0
 @atestisthis: Opps yes, remover. All I know is the 50/50 works better than any store penetrant I tried. I believe the ATF acts as the transport and lubricant by not allowing the nail polish to quickly evaporate. NP remover is virtually all acetone. Cheers. Thanks for the correction.
  • 1 0
 @SATN-XC: there are tons of suggestions that work for this. Mine from experience, is I use olive oil for delicate things that need unf*cking, and WD40 for everything else needing unf*cking.
  • 2 0
 Aluminum has a much higher coefficient of thermal expansion then steel and carbon fiber composites. I would suggest trying a super cold aerosol spray on the seatpost. The aluminum post should shrink much more than the steel or carbon fiber when chilled which might allow it to break free. I would try the spray along with penetrating oil.
  • 4 0
 Market: WE NEED TO MAKE E BIKE SPECIFIC PARTS BECAUSE OF THE EXTRA FORCE

Us 225lbs people who have been riding normal bikes forever: Yeah ok...
  • 1 0
 How many of you are running 15-20% fork sag? I've always heard 25-30% is the number to aim for with the fork, so I've always been running that. Have I been running it wrong all this time?! I do have to use a fair bit of low speed compression to avoid fork dive but I very rarely bottom the fork out, even on 6ft+ drops. Interested to hear what other people are running!
  • 3 0
 25-30 f&r when stood on your bike in riding position
15&30 f&r when seated
  • 1 0
 @NZRalphy: that makes sense, thanks
  • 3 0
 I'm running 15% while standing yes.
If you want to charge the front wheel and have front tire grip, 30% is way too much.
Try reducing sag to 20% and reducing LSC. If you have tokens try removing some.
  • 1 1
 Reach, Stem-length, Effective Top Tube, STA....you can't really talk one without the others. I see alot of people trying to fix the "feel" of a bike by increasing the stem and I don't like it. I hate long stems because you start to feel like you're steering a wheel thats underneath you instead of out in front. Then things get more twitchy because you're doing the opposite of what is being accomplished when a company makes a bike with a long front center, short-stem, slack HTA and steep STA.
  • 4 0
 Doing the opposite of what is being accomplished is part of how Murray got EWS 6th. I wonder what size Enduro he chose
  • 1 0
 @ceecee: I'm not sure what his situation was exactly, I'd be curious to know. I don't think there's a one-size-fits-all stem length by any means. But I'm just seeing some people in my neck of the woods wanting to update their bike to today's reach standards by adding 20mm to their stem length because their reach is "supposed to be longer" now. Orrrr, I'm swapping to a 20mm longer fork and adding 10 spacers to my stack height so my reach is shorter, I'm going to get a long 70mm stem to fix it....no good. Again, tweaking is good, trying to change the bike size is bad. I actually did add some stack height on my fat bike due to a fork steerer that was cut real short, had to add an extension and my reach did in-fact decrease. I changed from a 45mm stem to a 50mm. IMO just a "tweak".
  • 2 0
 @yupstate: @fire-munki wants to ride XC on his 140mm. He'll be fine. Those people in your neck are not serious hobbyists
  • 1 0
 @ceecee: yeah I'll agree 140mm is not a good xc bike but as a stand in until the pennies down the sofa add up it'll have to do!

Steering hasn't been buggered up to much either which is good.
  • 1 0
 @fire-munki: I've a downsize 160mm that goes across country with gusto, but don't race it. Charge the rough bits. Brake pads don't wear much. Hopefully you're little more than 178cm
  • 1 0
 Not fork related but do coil shocks sometimes make a knocking noise when going through travel? The spring isn’t binding and the bushings seem fine.
  • 4 3
 I have never had anything Ebike related keep me up at night. This article must be geared to people that subscribe to Outside.
  • 1 0
 I run my shock at 20% sag, though it could have something to do with riding on the shore and having only 140mm or rear sus travel. I am also pretty light less than 150lbs.
  • 1 0
 I've had great experience with WTB saddles and have helped to greatly reduce pain for long days on the bike.
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