# Suspension SETUP, a 'how to' guide...

PB Forum :: Mechanics' Lounge
Suspension SETUP, a 'how to' guide...
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Posted: Sep 14, 2020 at 23:37 Quote
 R-M-R wrote: Pandora's box ...First, we would need to establish whether how to measure the travel. In descending order of reasonableness:1. Vertical, with the pitch of the frame remaining constant2. Straight line between the endpoints of the axle path3. Aligned along the arc of the travelNote that Trust used method #3, which is where their "arc travel" came from. Disingenuous way to pad their numbers, if you ask me. Anyway ...The easiest way to do it is to model the bike in Linkage. That's how I generated the sag tables I provided to you. The accuracy will depend on the quality of the images used for the model and whether you interpolate the central plane of the bike.There's also a question of how to incorporate other sources of "travel", such as:• Tire compression, which is about a third to half the linkage travel• Wheel flex• Frame flex, which is more than you may expect

Wow ya you weren’t joking when you said Pandora’s box. I’ll check out linkage and see if I can figure that out. Thanks

 Posted: Sep 14, 2020 at 23:56 Quote Correction: the easiest method is to just trust YT's claimed travel!One of the European bike magazines measured travel and geometry on several bikes and found a few major deviations and numerous minor ones - assuming we trust the magazine's numbers, that is.

Posted: Sep 15, 2020 at 0:41 Quote
 R-M-R wrote: Correction: the easiest method is to just trust YT's claimed travel!One of the European bike magazines measured travel and geometry on several bikes and found a few major deviations and numerous minor ones - assuming we trust the magazine's numbers, that is.

Like according to vitalmtb new speci enduro has 176 travel

 Posted: Sep 15, 2020 at 1:43 Quote Surely the easiest way is to take the spring off/ let air out of your rear shock. Make sure you hold your frame still somehowTrace the rear axel path on a piece of paper and measure the drawn line?

 Posted: Sep 15, 2020 at 2:58 Quote Just chucking this in for fun, as I really don't think it matters a huge amount, but...I'd find some way to solidly mount the frame with both tyres on the floor, remove spring and fully compress rear suspension, then measure the distance from the lowest point on the tyre to the floor. This gives you the size of the biggest rock you can run over, ignoring any wibbly axle path wierdness.

Posted: Sep 15, 2020 at 7:00 Quote
 gabriel-mission9 wrote: I'd find some way to solidly mount the frame with both tyres on the floor, remove spring and fully compress rear suspension, then measure the distance from the lowest point on the tyre to the floor. This gives you the size of the biggest rock you can run over, ignoring any wibbly axle path wierdness.

That's the vertical travel method. High-pivot idler designs are very upset by this suggestion!

Seriously, though, I put this method as my #1, though there are reasonable arguments for methods #2 and #3 ... well, "semi-reasonable" for #3.

Posted: Sep 15, 2020 at 10:12 Quote
 R-M-R wrote: Correction: the easiest method is to just trust YT's claimed travel!One of the European bike magazines measured travel and geometry on several bikes and found a few major deviations and numerous minor ones - assuming we trust the magazine's numbers, that is.

Ya one of those magazines said the jeffsy had 143mm rear wheel travel. YT claims 150.

 Posted: Sep 16, 2020 at 11:46 Quote Can i use 7 wt oil over 7.5, I need a small amount and only rockshox makes small amounts on 7wt like 120ml, most of the 7.5's are minimum 250

 Posted: Sep 16, 2020 at 11:59 Quote Yes, absolutely. Some "2.5 wt" fluids are thicker than some "10 wt" fluids. Fluid "weight" designations are all over the map.

Posted: Sep 16, 2020 at 12:12 Quote
 R-M-R wrote: Yes, absolutely. Some "2.5 wt" fluids are thicker than some "10 wt" fluids. Fluid "weight" designations are all over the map.

thanks

Posted: Sep 16, 2020 at 13:08 Quote
 liamhutch89 wrote: Hi all, i'm on a 2021 Commencal Clash and so far haven't been able to dial in my rear shock's settings (super deluxe ultimate with 3 tokens factory fitted).I'm running 210 psi which gets me to the recommended 30% sag and i'm using full travel on most DH / freeride runs. I don't feel it get to the end of the travel but the rubber band shows that I have. All good so far, however i'm finding on steep dirt jumps the bike is being unpredictable, with a sensation of being stuck in the air (aka dead sailor), or being thrown forwards sometimes. I typically have good jump technique and can whip/flip/etc so I don't think it is that. My rebound is to the slower end of normal and i'm running my fork on the firmer side.I'm thinking it could perhaps be due to the high progression of 3 tokens combined with a progressive linkage, and I pump take offs HARD due to a long bmx background. I've noticed if I actively try not to pump hard to boost things the bike is more predictable. My previous bike was a capra with a coil shock and I didn't have this issue. Other differing factors are my new bike is shorter, it has 27.5 wheels (vs 29) and the front end is lower - its still high-ish but my Capras was very high. Whilst geometry could be part of the problem I feel that this would not give the unpredictability that i'm getting.I'm worried that if I try reducing tokens i will blow through the travel too easily. Could it be anything else?

I've somewhat resolved this by drastically altering the progressivity front and rear.

For some reason Commencal have shipped the bike with 3 tokens in the back on a progressive linkage and no spacers in the zeb which has a huge air volume (I.E. quite linear for air).

Ive removed all 3 tokens from the back, upped sag to 25% to hopefully mitigate bottom out and added two tokens to the fork. Bouncing around on my street the bike is far more balanced front to rear but I'm yet to test it on the trail.

Posted: Sep 17, 2020 at 0:53 Quote
 R-M-R wrote: Yes, absolutely. Some "2.5 wt" fluids are thicker than some "10 wt" fluids. Fluid "weight" designations are all over the map.

One more question, are there any difference between a normal fork oil and a shock specific oil? İ think there is not but im not sure

 Posted: Sep 17, 2020 at 7:42 Quote liamhutch89: That goes a long way toward explaining the imbalanced feel. Sounds like you're on the right track.Noeserd: I recall some "shock-specific" fluid saying they use substances that are more resistant to high temperatures and cracking. If this is true, it suggests two things:1. The shock fluid should be more durable.2. Fork fluids must be cheaper and/or more effective because if they were neither, the manufacturer would use the shock fluid for both.A shock designer once told me suspension fluids have to balance performance against durability. Fluids used in consumer car shocks, for example, are extremely durable, but not very good. Fluids for high-end racing applications work better, but need to be changed frequently. If this is true, it probably reflects the difference between a shock-specific fluid and a fork fluid.

 Posted: Sep 18, 2020 at 16:10 Quote I've noticed on my super deluxe ultimate that every time i push down on the seat, it seems to equalize the positive and negative chambers in the shock when going past approximately 10% travel. It's not quite as pronounced as when you pump up the shock and equalize every 50psi or so but it feels pretty bad. I don't know if it was always doing this (still in new bike honeymoon period) but it makes it feel sticky, like a notch at 10% travel. What's going on? If this is what air is supposed to be like i'm going back to coil!

Posted: Sep 18, 2020 at 16:20 Quote
 liamhutch89 wrote: I've noticed on my super deluxe ultimate that every time i push down on the seat, it seems to equalize the positive and negative chambers in the shock when going past approximately 10% travel. It's not quite as pronounced as when you pump up the shock and equalize every 50psi or so but it feels pretty bad. I don't know if it was always doing this (still in new bike honeymoon period) but it makes it feel sticky, like a notch at 10% travel. What's going on? If this is what air is supposed to be like i'm going back to coil!

Thats normal. Just a thing air shocks do.