4-Banger Owners - can someone help with a dimension?
Yep, I'm bugging the Banger owners again.
Short and sweet: I'm looking for people with original Rock Shox coil setups on their bikes, and I know there are a few of you here.
What is the range of trunnion-to-eye length that you can get with your bikes? I notice that my SID air shock from my 2000 has this length fixed at 5.5" (140mm). The original setup manual that I have for the 1999 Bangers (has the full range, actually) lists the range of adjustment as 5.28 - 5.66" (134 - 144mm) with 5.41 as nominal (137mm). However, the Super Deluxe that I have, taken off my '99 Homegrown 4-Banger, can't possibly do that range. It goes from 4 5/8" (117mm) to 4 7/8" (124mm). That would result in MUCH slacker head angle, and I'm not even sure that the tire won't hit the swing arm if I bottom out at those lengths.
Could one of you coil guys take a quick measurement of your tunnion-to-eye and let me know? Thanks!
Last edited by CTB; 05-07-2009 at 01:01 PM.
I thought maybe you guys would like to see why I'm asking this. Below is a picture of my bike with the two different shocks on it. The top pic has my 2000 SID shock on the bike, 140mm t-to-eye. The bottom pic has the Rock Shox Super Deluxe that came with my HG4B, set at the longest t-to-eye length I could make - roughly 130mm.
The yellow boxes are at the exact same angle - note how the head angle has changed to no longer be lined up with the yellow box with the coil setup. I'm estimating about 1.5° of change here.
Again, 130mm is way outside the range quoted in the Schwinn setup guide for this bike. I'd really love it if someone could take a quick t-to-eye measurement on their coil bike for me. Thanks.
146mm seems to stick in my mind, but I'm using a longer shock than stock (2" stroke).
Thanks, Baulz. Hopefully anyone out there with a 4B coil can measure theirs. Kenji? Lamparito? Anyone? I seem to recall Joemamad is running a SID on the back of his, so his would be identical to mine.
The difference in crown-to-axle between my Fox F100 and the original SID 100 is only 1/8", so that only accounts for about 0.2° of head angle. It's as though someone put a shorter version of the RS shock on my bike, but that seems pretty unlikely.
My stock 1.5" stroke shock is 139mm eye to eye. I found the bike to be a little slack setup like that with a 4.5"ish travel Psylo fork. The bike came like that, so I have not played around with different settings.
Why not just measure your head tube angle and go from there? To measure it easily, find a protractor which has a hole cross mark in the middle on the bottom like in this picture:
Then take a spoke and stick it through the hole. With the bike properly weighted (to account for sag) hold the bottom edge of the protractor up to the fork leg allowing the spoke to hang free, and read the angle. Depending on how the angles are marked, you might need to subtract it from 90.
So long as the tire doesn't hit or frame component doesn't hit at the extremes of rear suspension travel, you can have the trunion set where ever you like. It's nice because you can, to a certain extent, dial in what head angle you want, and account for different length forks.
I know what the angle is, within a degree or so. The top pic is around 70.5, the bottom is around 69. I see you've seen my other thread about the Fox shock, which I utilized to do exactly what you said - dialied in the head angle that gave the feel I wanted. I'm working on fixing that so I can have it back.
What doesn't make sense is that the shock you see in the coil picture can't possibly provide the dimensions that Schwinn spec'ed for the bike. I used the Linkage software to tell me the change in angle between the settings (around 1.5). The longest possible setting on this supposedly OEM shock is far shorter (and hence the bike is slacker) than Schwinn says it should be. It's also a LOT shorter than the SID air shock I have from my 2000 Banger. I'm just trying to determine if all the OEM coils were like mine and Schwinn just mis-quoted the specs, or maybe someone changed my shock long before I got the bike. Dude had it set up like a chopper when I bought it - 120mm fork, and about a 67° head angle - so who knows. As you said, "you can have the trunnion set wherever you like." Except in this case, I can't because the longest setting is still slacker than the bike is supposed to be. I'm going to ride this setting today to see how it feels compared to last week on the "normal" setting with the SID shock. I like reasonably slow, linear bikes, but this might be too far. I'm at around a 130mm t-to-eye length with this setup; I was running the Fox at about EDIT: 137mm, down from the stock 140mm.
PS: Good protractor picture. I'm saving that one.
EDIT: I stand corrected. I just looked at my Fox shock, and I was running that at around 137mm t-to-eye. Not a huge reduction in head angle from the stock 140mm, but enough to notice it for sure. (That is about 0.5° more slack than at 140mm.)
Last edited by CTB; 05-12-2009 at 12:32 PM.
smell my finger
Just measured a Super Deluxe that came with one of my frames, got 5.5" i2i at the longest.
Just took her out for a little spin this morning.
Thanks Joe! And now...WTF?!?!?! My Super Deluxe doesn't have a PRAYER of reaching 5.5". The one you see in the picture above goes to 130mm maxxed out (a hair over 5). Your 5.5 matches my SID's fixed length perfectly.
In that case, my guess would be it's not one of the OEM shocks, and the previous owner switched it out at some point. Without researching this more, I'd guess it might be off the GT LTS or STS which was a contemporary of the 4 Banger and also used a trunion mount shock but measured 120mm eye to eye.
Here's a picture I found of a GT LTS shock:
Bad Mech, I have two of those GT LTS shocks, but in Coupe Deluxe form instead of Super. I think they're even shorter than what's on the Banger, but you totally bring up a great point. I'm going to have to compare them to what's on my Banger.
I just realized I didn't give a ride report. I rode the bike last week with the coil setup, which was a first for me. I've only ridden a Banger with an air shock until now. It worked really well. Plush,and the head angle wasn't too slack. Very nice for my style, actually. It was a pleasant surprise. I threw on a couple more clicks compression, one click more rebound, and a little more preload from my initial guesses and it worked well.
With luck, v2.0 of the Fox shock is coming in a couple days...