Triumph Rat Motorcycle Forums banner

Lowering Bonnie by cutting spacer or re-setting fork tubes?

9K views 9 replies 5 participants last post by  beemerrich 
#1 ·
I've posted earlier on this topic but posting again because I a little baffled about what seems to be a real problem with one of the proposed methods of lowering the Bonneville.

I could simply reset the fork tubes in the triple clamp, although it does seem a little cheesy to me to have the fork tubes sticking up.

People like Delboy recommend cutting the spacer, but how do you do any preload that way? Even worse, if the forks ever fully extended rebounded from a hard bump, you would have no load on the spring at all since it is shorter than the fork tube. Seems unsafe to me.

Has anyone here done one or the other? Thoughts on the is best?

Thanks.
 
#2 ·
People like Delboy recommend cutting the spacer, but how do you do any preload that way? Even worse, if the forks ever fully extended rebounded from a hard bump, you would have no load on the spring at all since it is shorter than the fork tube. Seems unsafe to me.
You are correct, this method of shortening the forks relies on the weight of the bike to contract the forks a little and take up the space left by the shortened spacer. Bonneville OEM forks do not have any form of preload adjustment anyway. However, I do think that you might be over thinking this - if the front wheel went airborne the forks would extend fully and there would be no pressure on the spring, but when it came back down the spring would resume normal function. It is unlikely to be unsafe.

I suggest that instead of cutting the spacers, you make spacers of your own, with plastic plumbing pipe. You can experiment with various lengths that way, and the plastic pipe is also suitable to be left in permanently.

Lifting the fork tubes is the only other way of lowering the front end, unless you wanted to go by the proper route, which would be to trim off the tops of the fork tubes and have them re-threaded for the fork caps. The spacers are then cut to a new length or new ones made.
 
#3 ·
Over thinking...

Probably so about the unsafe issue. Feels sloppy, though, to someone attuned to pre-load. Net the current pr-load of 15mm or so, it is only a gap of 5-10mm at the lowered height with the shorter spacer.

I currently have RaceTech .90 springs in there now (I'm 185 lbs. dry), but she is only 130 lbs, so I'll just go back to the stock springs (.75) and cur spacers to leave it 20mm shorter than stock, same drop as the TEC shocks.

Yes, I use Schedule 40 PVC pipe all the time. Slick, easy and very adaptable way to tune the front suspension. I always wonder why people go through all the effort to cut the metal.
 
#4 · (Edited)
Trimming the fork tubes is not necessarily proper, nor is it the only other way. And it sure isn't the least expensive way. The correct way is to pull the forks apart, including the damper rod from the bottom of the fork sliders. Then you can either stack another spring on the top out spring, or make your own spacers out of aforementioned PVC tubing.

Taking away preload by cutting the spacers is NOT the way to lower a bike. Nor is cutting fork tubes and sliding the tubes up through the tre, since the tubes will still be retaining their same travel. This is a good way to end up banging the fender on the rectifier on hard compression. Or even worse, wrecking.

I have a thread somewhere in the past of how to do this the proper way. I'll try to dig it up and post the link. This way, the forks will retain their original point of bottoming out, avoid a hard bang on the fender. You will lose a little travel, but not really a concern for those of us who are short, since we're lighter in weight.

Here ya go!
http://www.triumphrat.net/air-coole...w-to-lower-your-triumph-twin-front-forks.html
 
#6 ·
Spring confusion

Trimming the fork tubes is not necessarily proper, nor is it the only other way. And it sure isn't the least expensive way. The correct way is to pull the forks apart, including the damper rod from the bottom of the fork sliders. Then you can either stack another spring on the top out spring, or make your own spacers out of aforementioned PVC tubing.

Taking away preload by cutting the spacers is NOT the way to lower a bike. Nor is cutting fork tubes and sliding the tubes up through the tree. Since the tubes will still be retaking their same travel, this is a good way to end up banging the fender on the rectifier on hard compression. Or even worse, wrecking.

I have a thread somewhere in the past of how to do this the proper way. I'll try to dig it up and post the link. This way, the forks will retain their original point of bottoming out, avoid a hard bang on the fender. You will lose a little travel, but not really a concern for those of us who are short, since we're lighter in weight.

Here ya go!
http://www.triumphrat.net/air-coole...w-to-lower-your-triumph-twin-front-forks.html
I read this pretty carefully twice. I understand the process you describe, but not the reasoning. How does taking adding top-out springs lower the height? And after doing all that, what is the impact own the length of spring and sag I need to set up top?
 
#5 ·
I agree with Bron. You should have set your sag when you changed fork springs, that is set according to rider weight. Sliding the tubes up in the triples is the most common way to adjust fork length. Changing top out springs is also a good way, but way more work. When anyone sees your tubes above the triples, if they are knowledgable they understand that is a good easy way to lower the front end. It also retains full fork travel and puts more weight on the front wheel when cornering and reduces rake a little, which makes the bike easier to turn in.
 
#8 ·
That helps. Got it.
 
#10 ·
When sliding the fork tubes up through the trees to lower the front end, just make sure you pull the caps/compress the forks to maximum to ensure you don't create a situation where you'll foul the fender on the lower yoke. This method allows you to lower the machine to the maximum extent without causing any sort of unsafe condition or risk to your paint.

In my case, I only slipped the tubes up enough to mount the clip ons above the top clamp, which left plenty of clearance between the fender and lower yoke...ended up putting it back to regain cornering clearance, but that's another subject altogether.

--Rich
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top