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Mark65
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Joined: 16 May 2008
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PostPosted: 16:37 - 09 Feb 2018    Post subject: Fork Springs Reply with quote

Hi,
Im after trying new fork springs as my CB500F is comfy with the pre load on halfway but dives easily when using the brakes, or hard when I get the pre load to 41mm, that's the best I get. They are progressive that measure 35x340 0.6kg in the 41mm showa forks, I have seen some ktech that are 36x336 0.9kg going cheap so my question is will the 36mm diameter be to big for the Showa forks and damage them?.
Thanks
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Fizzer Thou
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PostPosted: 19:18 - 12 Feb 2018    Post subject: Reply with quote

Do you own a vernier caliper?If so,measure the OD of the springs and the ID of the fork leg and see how they compare Thumbs Up

What weight fork oil are you using?What weight is specified for the bike?Have you tried adding some to each leg?

The K-Tech springs will be as good quality as ones from Ohlins.Are they straight rate or progressive?

You can add a spacer on top of the springs to take up the difference Thumbs Up Wink Thumbs Up

And how is the preload 41mm?Do you mean SAG or fork travel?
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Mark65
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Joined: 16 May 2008
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PostPosted: 16:59 - 13 Feb 2018    Post subject: Reply with quote

Fizzer Thou wrote:
Do you own a vernier caliper?If so,measure the OD of the springs and the ID of the fork leg and see how they compare Thumbs Up

What weight fork oil are you using?What weight is specified for the bike?Have you tried adding some to each leg?

The K-Tech springs will be as good quality as ones from Ohlins.Are they straight rate or progressive?

You can add a spacer on top of the springs to take up the difference Thumbs Up Wink Thumbs Up

And how is the preload 41mm?Do you mean SAG or fork travel?


Thanks for answering Fizzer, fork oil will be standard 10w with new springs or will try 15w if I have to use old ones, the length is within 4mm of originals so a spacer or two but I have pre load adjusters on it.
41mm is sag but the ride is harsh, yes I have a vernier, can I assume if the springs go in the legs freely they will be ok?, its only 1-1.5mm difference to the originals?. The springs Im thinking of buying are straight rate, originals are progressive.

Mark
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Pigeon
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Joined: 27 Sep 2012
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PostPosted: 22:56 - 13 Feb 2018    Post subject: Reply with quote

The originals are progressive, so the sag is a bit more tricky than simply measurement.

You've got 41mm sag, but that's possibly used up much of the 'soft' part of the springs movement. Which could explain why it seems harsh, even though the sag isn't showing its stiff.

Or the compression damping is too much.


The Ktech springs are probably going to be linear (do you know?).

Would try 15w with 0.9kg spring instead of 10w.

If you know the spring is 4mm short, then 4mm of spacers.

I put 36mm springs in to replace 35mm with about 2mm gap. Been fine.

EDIT:

Sorry, yes you know they are linear Thumbs Up

Have tried linear and progressive and will always choose linear. Personal preference is all.
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Current: 2014 GSXR-1000 L5 + 2013 Triumph Street Triple + 1998 Honda XR250R -- Prior: 1990 Suzuki TS50X, 1988 GP100, 1998 Honda CG125, 2011 AJS JS125-E2 (Jianshe JS125-6A), 2000 Suzuki SV650S.
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Mark65
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Joined: 16 May 2008
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PostPosted: 14:06 - 14 Feb 2018    Post subject: Reply with quote

Thanks, it seems that race tech springs are 340mm long which is about 40mm shorter than stock but they include material to make new spacers, the ktech ones im watching are only a few mm shorter so I will need to make new spacers or stay with the stock spring and try the 15w oil, I dont understand why the would use spacer so large with the stock springs. Stock spring below aftermarket. I may just try them anyway.
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Mark65
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PostPosted: 10:56 - 15 Feb 2018    Post subject: Reply with quote

I took a chance on the springs, so now i need to add 40mm to the spacer, should I just add a separate 40mm spacer with the Honda one or use a piece of alloy tubing?, Im struggling to find a short length of schedule 80 tube as this is thicker walled, any suggestions.
Thanks

Maybe Class E pipe will work.
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.......
Borekit Bruiser



Joined: 01 May 2017
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PostPosted: 15:22 - 15 Feb 2018    Post subject: Reply with quote

That spacer looks like a pretty simple part to knock up on the lathe. Send me a PM if you'd like something made to measure.
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Mark65
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PostPosted: 15:41 - 16 Feb 2018    Post subject: Reply with quote

garybee wrote:
That spacer looks like a pretty simple part to knock up on the lathe. Send me a PM if you'd like something made to measure.


Thanks, gonna take them off this weekend i think, get the new tyre next week, see how we go, apparently i need .5mm gap all round on the spring i have read, new springs should be here next week.
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