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Discussion Starter · #1 ·
Hi everyone...my first post after lurking for some time, so go easy,

I've got a '93 Bridgestone MB-1 I bought a couple years ago. I was so damn eager to get one of these that I bought a size too small (I blame it on the bi-plane fork crown). No problem, I thought, I'll just swap out some components. So I replaced the 150mm Softride stem with a 145mm titanium stem (IBS from Germany) and the flat Ritchey handlebars for a Profile riser bar with about 1.5 or 2 inches of rise. It looks cool enough but...

The fork flexes or bounces a lot when I apply the front brake. The headset feels fine so that's not the problem...it's definitely the fork. Needless to say this can be quite scary when riding down a hill.

Has anyone else had this problem (with this or any other bike)? Can anyone suggest a way to solve this problem? I'm going to put the original stem and handlebar to see if the bouncing goes away. I'm guessing the flex has to do with the new components; the Softride stem must have soaked up a lot of the flexing. Maybe having my hands up a bit higher makes the problem worse as well, but my hands aren't any further forward than before.

Thanks for any advice, opinions, suggestions, etc.

geedubbayoo
 

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Harmonius Wrench
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It's in the crown

You mentioned the "bi-plane" fork crown. If you have this on your bike, that's where you are getting your flex, and you will have to swap out the fork to get rid of it, but......DON"T DO IT! That bike was designed to ride that way, and it's part of the appeal of that model and brand, well......for some of us, anyway! Obviously, it's a problem for you.

I'd suggest getting something appealing that actually fits you better and possibly move this one down the road, or keep it as is as a part of a collection. No amount of handlebar swappage, stem this-and-that is going to make it right if the fit is way off, but then again, I don't know, I can't see you on it! ;)

Those are pretty cool bikes, I hope this gives you some ideas. Perhaps someone else will chime in with something better.
 

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Very common for the forks of the day. I had several unicrowns that had brake sutter. One flexed so much on pavement (at very low speeds) the tire would pop forward 3" at a time. It was fun to watch!

The forks not only increased the ride comfort they would bend in a hard crash to prevent or reduce damage to the frame. It was much cheaper and easier to replace a fork rather than a frame.
 

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Discussion Starter · #6 ·
maybe you're right...

Thanks GuitarTed and Shiggy,

GTed, it might be the case that I SHOULD pass this one on, because that hopping in the fork while braking scares me on descents. And no, I'd never get rid of that fork; I'd rather sell it with the bike first.

It could be that this is just the nature of this type of fork, as you mention, but it didn't have this bounciness before I swapped components. I have a feeling it might be related to the new components (I can test this by reinstalling the old ones). I have experienced this type of flexing on another bike, and it was caused by improperly set up brakes combined with a rim that wasn't true. As the bad part of the rim would hit the pads it would catch the brakes and cause a noticeable cyclic hop, especially on a hill when I had to brake harder. I'll check the brakes and rim on my MB-1 when I can, but I think they're fine.

Shiggy, I see your point, but I have another bike ('89 Spec. RockCombo) with a uni-crown fork that doesn't have this problem. I also owned a '92 MB-3 (before it was stolen) that had a uni-crown as well, and no stuttering there either.

I'm inclined to believe the bounciness in my fork is due to the frame being too small for me (I'm 5'9", it's a 49cm and I probably need a 52cm) and possibly a wobbly rim.

Thanks again everyone,
Geedubbayoo
 

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bushpig said:
It is ironic then that now older rigid forks have tended to appreciate in value relative to frames.
Probably for the same reason though. The forks are more rare because they bent. The frames survived because the forks bent first.
 

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clueless
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... to use an ibs ti stem in this length with riser bars is not the best idea. ibs ti parts are known in germany for their tendency to fail :eek: look for some nitto, ritchey force or salsa cromo stem to be on the save side.

the braking problem could be relieved by trying other brake pads. I had a similar problem with my bontrager comp fork, dc 986 with wtb dualcompound pads, used and some years old. horrible, a nightmare... After mounting new koolstop eagle claw 2, grey compound, and some cleaning/slight sanding to the rims, the brake stutter nearly disappeared.

ciao
flo
 

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I have the same fork on a '94 MB-1. Yes there should be some fork flex by design, but there should not be any studder from braking. My guess is that either the headset is loose, or the headset crown races are not super tight. If the front end is bouncing back and forth when you brake hard, there's something not quite right.
 

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Don't blame the fork !

floibex' example of a flexing Bontrager Composite prooves clearly that the fork is NOT the problem - or better: the REASON for it.

Everything starts in the brake system - as I experienced back in the days riding my '91 MB-1 with Ritchey's Logic fork, DiaCompe's 986 cantilevers and Ritchey Vantage Comp rims.

It could be the brake pads (too flexy). The cantilever arms (flexy). The rim (uneven brake surface). Even the tire's tread can make a difference.

I changed the front wheel and everything was fine.

My suggestion: change the brake pads first, because that's the cheapest attempt and might even improve brake power. If that doesn't help, borrow a friend's front wheel (or take one out of your many other classic rigs).

Good luck,

:)
 

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which fork?

This probably is not the Ritchey Logic unicrown. I'm thinking it is the luuged flat crown slotted fork that they came out with one year and made a big deal about it in the catalog. Yes I have it but it's at home.
 

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Doesn't matter which fork !

That's what I wanted to say: The problem is NOT the fork - neither a Bontrager (reasonably stiff) nor any Ritchey Logic or lugged model.

I had the same front end vibrations this summer, using a Fox RC36 (very stiff) with a new disc brake. Its (wave style) rotor needed some brake-in miles ... and everything was fine.

:)
 
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