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forks dive when front brake is applied

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06 yamaha wr450

i weigh 175 and the spring rates are good enough for me...per Racetech recommendations.

when applying the front brake the forks dive, basically close to bottoming out. will changing the shim stack and heavier oil affect this? my race sag(75mm) is about a whole inch too much. i was able to set the race sag on the rear shock, just not sure how to do the forks...

anyone?

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It's really a valving issue with that bike. It needs a good base and mid-valve set up. Once that's done, it'll work great.

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Well, you have two choices: 1. You can send your forks to a good suspension shop and have them do the work, or 2. you can go to your local Yamaha dealer and look up the base valves for (example) a YZ426F. Purchase them and then play around with the valving yourself.

HOWEVER: Maybe someone else will chime in because I don't recall if the 06 had the "check spring" base valve or if that was after 06......If it had a "normal" base valve (like the one in the 426), then you just need a good revalve of the stock parts.

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75mm of sag is part of the problem

Well, true.....but "per Race Tech" the springs he has are correct for his weight.....

:busted:

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Not sure where you guys get that 75mm of rider sag is too much ? That is correct with 11.8" or 300mm of fork travel. Rider sag should be 25% of available travel . If his static sag is 35-45mm then that is fine. If you don't have enough rider sag the front will push badly in the flat corners. MXers can get away with less rider sag because they have plenty of berms. Offroaders must have the forks setup for corners by diving. If diving too much raise your oil level and/or increase your compression damping. Make sure you have approx 33-34% of available rear wheel travel in rider sag. Not enough rear rider sag will make the front oversteer in the corners. Too much rider sag and the front will push.

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Fork compression too soft? Turn your compression clicker to make it stiffer... Does/will it help?

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this is going to be setup for supermoto....the majority over at smj.com were saying 45mm race sag for forks and 75mm race sag for the rear shock. i know i'll have to dial in the compression and rebound settings, the rear feels fine, just the forks are unpredictable in the corners! and when the front brake is applied it just dives!

i'm assuming this means the valve lets too much oil through?

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If diving too much raise your oil level and/or increase your compression damping.

Wow, I'm with you here....I would have thought this would have been the first response - at least that was my first thought. Interesting to get such a wide range of responses when this would have been the easiest and first approach to try.

Only if this didn't work would I suggest going to new valving.

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thank you i will try that first! how much should i add? 10-20cc each?

I'm sure you can find out or search how many cc's are in there now, but add 10cc's - 5 or 7 weight should be fine.

Also, add 2 clicks to your front Compression just as a starter. No idea what your clickers are set at, but to help the front from diving you may need to go more than two clicks stiffer on the compression. Adding 10cc's and increasing the Compression 2 clicks, then ride, you should feel an improvement. The only question will be - is it enough, but you'll see real fast how it's working....Then add 1 click at a time and test from there.

Hope you make out.

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Your forks are too soft and your rear is too high. Rear sag should be about a 3rd not a quarter. Lower your rear at least to 95mm of sag and test. Thats the easiest thing to do! You might of got 75mm of sag from someone that has had there bike lowered for supermoto already.

Read you manual or get a local tuner.

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this is going to be setup for supermoto....the majority over at smj.com were saying 45mm race sag for forks and 75mm race sag for the rear shock. i know i'll have to dial in the compression and rebound settings, the rear feels fine, just the forks are unpredictable in the corners! and when the front brake is applied it just dives!

i'm assuming this means the valve lets too much oil through?

I don't know much about supermoto but I imagine that your suspension travel is shorter than offroad or MX. What exactly is your wheel travel front and rear ?

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thank you i will try that first! how much should i add? 10-20cc each?

Raise your oil level to max . Probably about 110mm or less.

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Wow, I'm with you here....I would have thought this would have been the first response - at least that was my first thought. Interesting to get such a wide range of responses when this would have been the easiest and first approach to try.

Only if this didn't work would I suggest going to new valving.

The OP asked if changing the shim stack would help the dive that he experiences under braking. The answer to that question is "yes". The WR has basic set up issues for anyone of "normal" size. Adding oil will not help the "diving under braking" issue - that's a valving issue. Thus, I suggested that he have the suspension revalved. Especially now that he's posted that it's going to be used for supermoto. The stock valving that is designed for easy trail riding will not work at all for supermoto.

:busted:

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