[ChrisRobin]

Just some random thinking today....

Even though the bumper can compress a fair bit, I don't see it becoming thinner than say, 1/4". If we take a popular frame like the Turner DHR with 8.5" of travel, the 3.0 stroke shock with a fully compressed bumper really reduces the effective stroke to roughly 2.75. That means the DHR would only get a REAL 7.8" of rear travel at full bottom out. To me, that's a fairly big difference (the V10 loses closer to a full inch)

I know you're not supposed to be bottoming out everywhere but at the same time, frame builders are advertising a certain amount of travel that you're never going to physically get... right?

 

[DHS]

pretty damn far. i've seen them compress to 1/8 their size

 

[davep]

Pull a bumper off and stack about 1200 - 1500 lbs on it....see how thin it gets. That is how much force the bumper can see..


They do get pretty thin, especially the ones on DHXs as they are soft and thin to begin with. The bumpers off of a fifth were bigger and stiffer...would be a great cheap upgrade for a linear rate frame if yo could find one.

 

[Eren]

and thats why the 3 bumpers that come with vivid will be great!

 

[Pip3r]

back before i had any clue what i was doing my friends and i used to cut our bumpers down just for that reason, to get 'more travel' ahah.

 

[karpi]

the avalanche ones are pretty big, but at least it just makes it all that more smooth

 

[TWeerts]

some frames dont need bumpers: the sx trail comes to mind. and in that case, you are getting the full 17 cm.

 

[Steve M]

some frames dont need bumpers: the sx trail comes to mind. and in that case, you are getting the full 17 cm.

Why exactly does an SX trail not need a shock bumper?

 

[djamgils]

marketing slogan: we made the frame flexy so you dont need bottom out bumpers to save weight.

what if the bumper compresses to 2mm, with a 3:1 leverage ratio this would mean you miss out on 6 mm of travel. That is 3% of a 200mm susp stroke. You could argue if that is so bad.

Ever checked if your susp stroke is the same as the manufacturers claimed it would be?

 

[Transcend]

some frames dont need bumpers: the sx trail comes to mind. and in that case, you are getting the full 17 cm.

uhhh, no.

 

[Jeremy R]

some frames dont need bumpers: the sx trail comes to mind. and in that case, you are getting the full 17 cm.

he he,
the bumper on my sx trail has taken more hits than a jersey working girl.

 

[binary visions]

some frames dont need bumpers: the sx trail comes to mind. and in that case, you are getting the full 17 cm.

I know, I know, I'm probably just being silly, but I could just swear that this crop of a stock photo from Specialized has a bumper in it.

Maybe someone at the marketing department just photoshopped it in.

 

[kidwoo]

Must be the completely vertical axle path and fully active suspension immune to both pedaling and braking forces that causes spec bikes to need no bumper.

Gawd dayum those things are magic.

 

[ChrisRobin]

what if the bumper compresses to 2mm, with a 3:1 leverage ratio this would mean you miss out on 6 mm of travel. That is 3% of a 200mm susp stroke. You could argue if that is so bad

2mm is pretty thin... especially since the bumper has no where to expand since it's sitting in the middle of a retainer coller and coil. Although I think I'm being too picky/critical so don't mind me.

Ever checked if your susp stroke is the same as the manufacturers claimed it would be?

Ah yes! Good point! My old Fox RC was exactly 2.75, my Romic is a full 3.0 and when I had a Stratos El Jefe, it was 2.75... then you would add on the retainer collar, bumper, you were down to 2.5 of useable stroke (very similar to Avy).

 

[djamgils]

2mm is pretty thin... especially since the bumper has no where to expand since it's sitting in the middle of a retainer coller and coil. Although I think I'm being too picky/critical so don't mind me.

I forgot about that. Never looked at it closely but I guess it isn't massive rubber but something with air inside it (porous foam or how do you call it)
But is it really necessary to use a bottom out bumper. How much reduction in force will it realise.
What is better, to slow down the piston on damping and spring or on a reduced stroke with a bumper.

 

[General Lee]

i have bottomed out a bottom out bumper before; it doesn't feel good.

 

[LukeD]

back before i had any clue what i was doing my friends and i used to cut our bumpers down just for that reason, to get 'more travel' ahah.

the RS rear shock on the old DHi had a big plastic piece under the bumper which limited travel! that got shaved down back in the day haha

 

[TWeerts]

I know, I know, I'm probably just being silly, but I could just swear that this crop of a stock photo from Specialized has a bumper in it.

Maybe someone at the marketing department just photoshopped it in.

ohhh, im sorry everybody, i didnt think you would all get but hurt when i said my sx frame has no bumper...the frame does not. the shock does. i thought the guy who started this thread was refering to the bumpers on frames, such as any of the vpp bikes.

every one calm down.

 

[toodles]

i thought the guy who started this thread was refering to the bumpers on frames, such as any of the vpp bikes.

They have bumpers on the frames?

 

[ChrisRobin]

They have bumpers on the frames?

Yeah that drew up some confusion on my end too.

 

[TWeerts]

nvm, its actually for when it tops out. my bad. but i thought you were refering to frame bumpers in the first place.

 

[ChrisRobin]

nvm, its actually for when it tops out. my bad. but i thought you were refering to frame bumpers in the first place.

Ahhh, gotcha...

 

[- seb]

the RS rear shock on the old DHi had a big plastic piece under the bumper which limited travel! that got shaved down back in the day haha

Yeah, the RS shock on the old DHis (mine was a 2001) is a 3" stroke, but with a 0.25" rigid bit of plastic behind the bumpstop. The bumpstop is also very solid, I imagine it only compresses 50% or so, meaning the real effective stroke is about 2.5".