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.
Press Fit BB Creaking?Question: Atjr asks in the
All Mountain, Enduro & Cross-Country Forum:
had a LBS replace the BB on my 2017 Rocky Mountain TB Carbon. It didn’t have any issues before. Now after about 1 mile I’m getting intermittent creaking. It was about 6 months ago and I had it replaced with the same Shimano stuff. I only put about 20 miles on it since. I know if I go back there they won’t do anything for me. I’m thinking they didn’t do it right. Should I find a different LBS and buy a better BB? Or is it something a good mechanic can fix without replacing it? | If you had something replaced and put no more than 20 miles on it, it shouldn't be causing you any issues at this point. The first question I would ask you is if you're sure it's the bottom bracket? A lot of other things creak and it's easy to blame the 'ol press-fit BB but, a lot of times it can be a loose shock bolt, pedal, saddle, or something else.
If it is in fact the BB or you can't precisely diagnose the creak, you should be able to take it to your shop and have an open and candid conversation with them about what's going on. If you don't believe they'll stand behind their work, then why did you go there in the first place? It's hard for me to imagine the situation where you would need a new bottom bracket, but if the wrong type of grease was used or something wasn't done correctly it could be making noise resulting from the installation.
Bottom line is, you don't need a better BB. You may need a better mechanic, or you may have something totally different wrong with your bike, but I'd always recommend starting where you left off and if that doesn't work, then it could be worth considering a second opinion. |
Would you buy a bike without testing it first?Question: @kenglish asks in the
Beginners Forum:
Is it just plain stupid to buy a bike without riding it first?.... | No, it's not plain stupid but, it's a good idea to try before you buy. It's harder now than ever to do that with demos and social activities few and far between, but I'd strongly suggest at least riding something similar.
What's a great bike for one person isn't always that good for someone else. That's something we always take into account when reviewing a bike or product here at Pinkbike. A bike that I recommend to you may not be at all what I would choose myself and vice versa. If you can at least get on a bike with a similar geometry and suspension platform to what you're looking at buying, you will be able to give yourself an idea of how what you want may ride. That, coupled with some expert reviews or opinions from friends you trust who know your riding style may help you ensure that what you're getting is a great fit and something you'll be happy with for miles to come. |
Between Sizes...Question: @Jrljr777 asks in the
Beginners Forum:
Looking for some advice. I'm between sizes (I'm 5 foot 6 inches tall) looking at either a small frame 29er or a medium frame 27.5. Not sure which one to get.  | Manufacturers have made a lot of changes in their sizing recommendations across the board over the last few years. The tricky part is that sizing isn't entirely consistent between brands - what one company recommends isn't always going to be the same as what another one suggests.
When you're looking at a small 29er or medium 27.5" bike, the first thing I would ask is if it's the same brand? A lot of 29ers will now fit riders down to 4'11", so you can't just assume that a small 29" frame is going to be bigger than a medium 27.5" frame. Most brands try to keep their size suggestions consistent, regardless of wheel size. Keep in mind the year of the bike you're looking at too. If it's current, that's easiest. If the bike is a few years old, do some research and see where the sizing lands you in regards to wheel size. At 5'6", I would personally almost always suggest a medium whether it's a 27.5" bike or 29" - I think you will be too crowded on a small, but there could be exceptions.
Good luck in your quest for a new bike and if you can, give both a spin before you buy! |
Keep Breaking SpokesQuestion: @BUNKER63 asks in the
Mechanics' Lounge:
I am running ENVE m60 HV with Chris King hubs that are about 2 years old and CushCore that was added 6 months back. I have broken a spoke the last 3 times I have ridden. Nothing has been caught on the spokes when riding, it's the impacts that are snapping them right at the nipple. I was wondering if wheels needed to be rebuilt after riding on them for a while even if the wheel is still true. There is no damage to the rim or hub either. Any tips would be helpful. | Nothing is confidence detracting like consistently breaking spokes when you're out for a ride. Especially when it's happening on your wheels that are worth a couple thousand dollars. Without having more information on how you ride, how much you weigh, conditions, etc. it's hard to make a definite suggestion.
I'd start by checking back in with whoever is replacing the spokes in your wheels or, if that's you, the original builder and see if they have a suggestion. Your spokes may be overtensioned, and if you break one sometimes it turns into a chain reaction nightmare. Everything has a fatigue life and one spoke breaking puts more stress on the others and then it's a downward spiral. As suggested, you could have some corrosion at the nipples, and if that's the case you're due for a rebuild with fresh spokes and nipples. With any wheels, it's critical to have your spoke tension in an acceptable range and if you've by some chance just been tightening loose spokes without checking tension, that can throw things off too and lead to spokes fatiguing quickly.
One last note- I'm guessing this is a rear wheel, but you should get your front wheel checked while you're at it. If there's corrosion, it's likely to be in both places. |
159 Comments
I am supporting a bike company.
A bit of Xtra for my family.
May your tires always flat and your derailleur forever skip
Derailleurs are for kitties. Singlespeed all the way.
Where i live he would be close into getting his price, while at the same time what i want and can't get is available down where he lives
For those of us who aren't "bros" or know the guy behind the counter, the service is usually beyond bad. When the guy with the creaky BB says "I know if I go back there they won’t do anything for me" - he's probably right! Or if they do, they'll charge him to look at it.
And as for always test riding before you buy - LOL! Good luck with that BEFORE the pandemic.
So next year, take my new bike build to another shop... pick it up and the mechanic obviously had no idea what "super boost' spacing was... spacers on the wrong sides and the chainline was all f*cked up and rubbing on the chain guide. Dude... the SRAM puts a very specific document that fully outlines compatibility and how to install that is the third hit on google when you search "sram dub super boost". I fixed it and called them back to speak to the mechanic so I could educate him on SuperBoost.
And these are supposedly shops that specialize in high end enduro/freeride mountain bike service and sales. I think next time I will just take a day off or whatever to take the time to do myself.
I will say though that before the pandemic... I was able to demo 5 different bikes I was contemplating buying. My local shops do... or did have pretty good demo programs.
The front pads never bedded in properly. When I called about this issue the mechanic on the phone told me they bed all pads and set up brakes perfectly before sending a new bike home. He obviously wasn’t aware that they knowingly sent me home with a bad bleed to begin with and his assumption they bike was sent out the door with perfectly set brakes was incorrect. I’d rather buy new pads and deal with it myself than continue to deal with that kind of chicanery. And lesson learned i will never try to save a few hundred $ by buying a complete bike again just to have to deal with a sub par build on my brand new bike.
Lots of terrible shops out there but the good ones are worth their weight in gold!
How come our pressfit hub bearings; pressfit frame bearings don’t creak... until their worn at least)
If your lbs doesn’t do that then go somewhere else
TLDR: the principles behind PF BB's aren't the issue, the execution is.
For a small/med size shop, margins are usually around 15-20% all said and done. That’s not counting shipping, building the bike, etc.
Backed the tension off a bit from the recommended spec and no issues since - We Are One wheels.
Which would you say is the weak point in the system:
a) Hub
b) Steel Spoke
b) Carbon (in this case) rim
c) Aluminum nipple
Unless you have garbage rims, the aluminum nipple is the weak point in the system by design. Aluminum has no fatigue life so it will always fatigue to a point of failure. Exceeding recommended tensions will accelerate this.
I had some cheap gravel wheels that were doing the same thing and the guy who taught me how to build wheels (he is now a DT Swiss tech rep) told me they were over tensioned and to start saving for a new set. Once they are over-tensioned like this, you cannot simply reduce the tension or they will be under-tensioned, you basically need to rebuild with fresh spokes and nips.
so saying they never break from overtension is simplistic and inherently not true. in fact, even in an undertensioned wheels, they break from being over tensioned momentarily! but yes, even tension uber alas!
As far as I can tell there are a LOTS of rims that CANNOT exceed what's labelled as there max - probably more that cannot than can. Some can't even tolerate their suggested max. From what I have seen come though the doors of a couple of shops I have been associated with, RaceFace rims go whacky before you reach their max tension and bulge around the spoke holes. Stan's and several others will develop waviness and eventually cracks. It has been our practise to target 10-15 kgf under the max for many rims. Some wheel builds, especially with offset spoke holes, tolerate a lower max tension well because the low side has been brought up closer to the high side, and it's the low side that we are concerned most with anyway, right? After all, as you say, spokes fail from being under-tensioned, and it's the low side that would be under-tensioned the most.
Add to that, that there are also specified max tensions on hubs, that you seem to have totally skipped and not mentioned. There are a number of hub manufacturers that will not warranty hub beyond their specified tension limits. Most I know if stop at 125 kgf, so while some alloy and carbon rims may have a sticker that says 130-140 kgf is okay, it often isn't.
IMHO, 105-115 kgf is a very safe place to be for most rims. Some like Stan's older generation mtb rims or very light carbon rims require even less. To make the blanket statement that you should always work to the recommended max or in the 120 kgf zone on a regular basis is a bold and dangerous statement. And I definitely wouldn't go above it in my limited experience as there seems to be no benefit, but a lot of risk.
@hardcore-hardtail You guys are wrong in saying the alloy nipple is the weak link here. Not if built right. Perhaps over time they may become so especially if low quality products are used, but they don't start that way. I have been fortunate enough to have worked with some good mechanics who have demonstrated these things to me in real life, as mentioned above, and I've built 40 or 50 pair myself under pretty good supervision.
Easy to demonstrate this as I mentioned, in a load jig. The spoke will fail before the nipple. I've watched this with my own eyes. Mr. Hardcore just doesn't like being wrong.
But ally may see an early grave if they aren't made from quality alloy and don't have a good anodization treatment. Corrosion is a dog, but with good nipples comes corrosion resistance. On the good alloy nipples - hint for Mr. Hardcore - DT isn't making them!
Anyway, I agree fully with your original post, and this one as well. There is a lot of bull out there. And a lot of people just repeating what they hear without doing the work and testing to see the results for themselves. I'm familiar with Mould, and have read lots of literature from Brandt, Brown, and Musson. Brandt was the most interesting of them to me, only because I think he had several flaws in his book (and I'm not the only one to think so) and he went down ardently defending himself against his detractors. All in all though, the summation of these works is a great body of knowledge. That said, there are many very experienced wheel builders creating new literature and bodies of work currently that are great as well. We live in a great time for learning not only from the peers in our shop space, but peers all over =). You just have to be careful who you are sponging up information from, as you have pointed out, there is a lot of bull out there.
Really I think experience counts as much as reading; learning how different rims react to tension, and seeing the results with our own eyes, versus chirping out random boiler plate tension numbers and making blanket statements for all builds, that counts in my books.
Demo events are fine, but trying to demo a bike is often difficult, esp if it's a popular bike. Even then,. what are we talking about for a demo,. parking lot, five hundred yards on the trail?
I balk at buying boutique, like the Cavalerie, but I've bought Lenz, Guerilla Gravity, Foes, and now Forbidden without a single demo, and I loved them all!
If somebody's an absolute beginner then they likely don't know the "difference" between a 120mm light trail bike & a 150mm borderline-Enduro bike, let alone what's good for the trails they enjoy riding.
This was pre covid... I'm sure those bikes are sold now.
As to creaks, check pivots and shock bushings. Sseat and seat post, BB/chainring, pedals, even headsets can creak, but most of mine have been pivots and bushings.
1. Less large demo events, if any due to you know what.
2. Some dealers may see no point. They barely have inventory to sell, let alone to dedicate to test rides. And if the dealer does have decent inventory (I've seen some) why would they want to make half their bikes "used" by letting them be demoed? Ok great, you demoed that SLX aluminum build and loved it...we'll have that size L, Carbon XTR build here for you sometime in January 2022!
Also, I only have wheels built with brass nipples by two super-expert builders...minimal weight penalty for massively increased reliability relative to aluminum nipples (particularly as I suspect aluminum oxidation can cause increased abrasion with the spoke threads, as well as some level of galvanic corrosion on steel spoke threads if/when the alloy nipples starts to oxidize with moisture).
The local specialized dealer is the only shop that regularly has demo bikes, and they were generous enough to let me take out an Enduro for a four day trip to Derby as nobody else had it booked in. Giant do a big demo day at a local MTB park once every couple of years, but the shop haven't had any demo bikes in ages. The local Norco & Merida shop and the Trek dealer let you do a car-park test ride but likewise don't get any demo stock from the importers. For anything boutique, you're laying down cold hard cash sight unseen.
Hardly anyone does organised demos here, so most of the bikes I tried before my last purchase (Remedy, Hightower, Megatower, SB150, SB130, Strive, Spectral, Optic, Reign, Stumpjumper) were borrowed from friends, or from complete randoms of similar height & weight I met on the trails who agreed to a 5 minute swap. "Nice bike mate, I'm looking for a new one, what do you think of it? If I can keep up with you, would I be be able to have a ride of it when we get to the last set of berms/techy uphill switchbacks/off-camber rock-garden?". Rode close to $50k worth of bikes in a single day in Derby (twice voted EWS race of the year) without paying a cent just by being friendly to other riders.
The last 10% can only come from a test ride. Whether it's around a bike shop parking lot or out on the trail. There are nuances such as how the bike feels and then the overall inaccuracy of geo charts posted online that come into the equation and muddy up the waters.
I know this sounds elitist, and at the same time defeatist (with current pandemic supply reality factoring in), but these bikes are a huge purchase decision. Only once you've bought one and had regrets, will you end up resigning yourself to almost never buy a bike without being able to confirm it yourself. It truly sucks to plop down cash and then realize you're on the wrong size, or that the bike works on paper, but something about it doesn't work with your riding style and you're sent chasing your tail.
The good news? It's pretty hard to find a crap bike these days. The bad news? The devil is in the details and since we're now paying used car prices for bikes... it's too big of a thing to just roll the dice on. Unless that is: You are a fanboi, a gambler or rich af. Then, yolo it and treat yoself!
bottom brackets rarely ever creak, the most common creaking points on a bike are the suspension pivots, headset, seatpost, seat, and pedals always try those first before checking the bb
Normally a couple inch between seat clamp and dropper collar. What bikes are you buying where you have to have a 75mm one.
Cannondale jekyll, intense tracer, lapierre zesty and now santa cruz megatower all with 150mm no problem. Surely you either have short legs for your height or you pedal with you seat too low.
Medium Scott BB to seat tube is 440mm + 170mm for crank+ 150mm dropper + 75mm seat = 835mm almost 33 inches.
...AND BOTH HAVE THE SAME LENGTH CHAINSTAYS
No, it's not plain stupid but, it's a good idea to try before you buy."
Me: [laughs in Australian]
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