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Wheel hop

Rob S.

Rob S.

Forum Guru
Past Site Supporter
I have a tendency to go too fast on the streets (make a light, etc.), which necessitates having to slow almost to a stop rather quickly. My rear wheel hops, the whole bike shudders and I'm on the verge of losing control.

The front has Race Tech .90 springs and no air. The rears are set to 4 (spring preload?).

What keeps surprising me is that in this situation Suzi is handling worse than my 1973 Z1. I used to be able to fly at an intersection, lock up the rear wheel (drum brake), and make a 90 degree turn with no sweat.
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Just happened again. I was coming off a highway, and the ramp was long enough for me to come off the brakes, but that had no effect. Just kept hopping.

I believe I now know the purpose of a slipper clutch.
 
Though rear wheel hopping, I would check out your front disks.
Could it be that a front disk is bent and even though you are letting off the squeeze the piston is releasing slow enough that the bent disk is still grabbing at bend and lifting the rear?

I had rear wheel hop from old worn shocks but while taking curves at speed it would start to bounce.
Never did it while stopping in a straight line.

With my shocks set at 3-4 my rear will occasionally make a very quick hop or two in a tight turn without brakes applied but it is just a quick hop without really loosing traction or any control. (At least it feels like a hop)
In that type of hop it is a bit of a surprise but without any loss. (hard to describe)
 
Another quick thought.
Spring in rear broke in tighter coils.

Time to ride the Harley:pirate:
Give up on speed:rolleyes::topsy_turvy::devilish:
 
dorkburger said:
Did it do this before the accident?
Click to expand...

Yes. About a tenth of a second before the accident. :xsmilie_mrgreen:

I was riding today with an Aprilia Tuono. I know it's trouble to expect 1982 state-of-the-art to perform like today's best, it just bothers me that in this respect she handles worse than my '73 Z1.

I'm ready to go for a new rear set up, but I don't want to spend $1,000. What would be the next best after Ohlins?
 
No way that bike handles worse than an old Z1. Swing-arm in solid shape, shock working at all?
 
GS1150Pilot said:
No way that bike handles worse than an old Z1. Swing-arm in solid shape, shock working at all?
Click to expand...

It's only in this one situation, hauling down quickly from high speed, that it seems worse than my old Z.

Swing arm certainly looks solid enough, especially compared to the old Z. I just sat on her and the top, bottom and middle of the springs compress.

I'm wondering if it's related to the anti-dive. I don't really know if they're functioning or not, but the hopping seems to start when the weight is transferred off the rear. I wish I had a thumb switch to turn the anti-dive off and on to rule that out.

I'm ready to do a complete overhaul of the rear suspension, but I'd be awfully disappointed if that didn't improve the hopping. BTW, I just had all the brake (and anti-dive) lines replaced with steel braided.
 
Rob S. said:
I'm ready to go for a new rear set up, but I don't want to spend $1,000. What would be the next best after Ohlins?
Click to expand...

http://www.wwag.com/step/800/112500.jpg

Bitubo shocks, race proven technology;

they all have selectable rebound presets, (top of the range, also have compression-damping adj.) and are fully rebuildable.

They are not as renowed as Holins, only because mgmt. does not invest as much in ads, but can assure you, they ride sweet...

Also come in chrome.

bitubo-bonneville.jpg
 
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Rob another thing to think about is if you are concerned its the anti dives just grab the demon speed block offs. It will be a cheaper way to rule out one possibility plus from all I have read the anti dives cause more issues than they resolve. Ill be running them once my coffers have refilled a bit.
 
Timothy from Demon Speed responded to my inquiry:

Hi Rob,

Sounds like you're unloading your rear wheel during hard braking. A common effect when the anti dive units are still active and set high (if that option is available). This effect is also increased when the forks are rebuilt and heavier fork oil is installed. Not a good feeling is it?

So you need to fix up your front end to get the back end to track properly. A set of my anti dive by pass plates will eliminate the sudden stiffening of the front end under braking. While installing them, this gives you the chance to wash out your forks and install a new set of straight rate springs, I prefer RaceTech stuff, and fresh fork oil. If you go to the RaceTech website it will give you a number of spring options and which weight of fork oil to use.

http://www.racetech.com/

If you can help it, don't use a progressive rate fork spring. They sound good on paper but not so good in action.

I have both black anodized and clear anodized anti dive by pass plates for your machine in stock. The price on my website includes shipping, so pick your color and I'll get them in the mail ASAP.

Thanks for asking,

Timothy
Demon Speed Racing

I answered:

Timothy,

Thanks for such a speedy response. I had new Race Tech .90 straight rate springs installed recently. I used to run the recommended air (7psi?), but was told by my mechanic that the crossover air tube was broken (I recently was flung off the bike because of the wheel hop), the part is no longer available new, and until a replacement is found, the forks won't hold air. Most of the GSR guys say not to bother with any air up front.

So bottom line, you're telling me the rear wheel hop is caused by the front suspension?

Rob S.

Comments, opinions, suggestions please? Thanks
 
You're running crappy stock shocks that were junk three decades ago and wondering why the rear end gets a little hinky?

Calling Captain Obvious on the oblivio-phone...
 
Lose the anti dives, you already have the new straight rate fork springs, what weight fork oil did you use. Might want to look into the cartridge emulators as well. Upgrade your rear shocks and check the run out on your front disks for chit and giggles. You'll be surprise what an accident will do to a bike after the fact once you start riding again, you'll start finding these problems.
 
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bwringer said:
You're running crappy stock shocks that were junk three decades ago and wondering why the rear end gets a little hinky?

Calling Captain Obvious on the oblivio-phone...
Click to expand...

Are you saying upgrade the rear and that will fix it? A lot are saying the problem lies in the front.
 
Rob S. said:
Are you saying upgrade the rear and that will fix it? A lot are saying the problem lies in the front.
Click to expand...

Reread all the comments just don't single out one. Most of are saying do a couple fixes on the front end AND upgrade the rear.
 
Rob S. said:
Are you saying upgrade the rear and that will fix it? A lot are saying the problem lies in the front.
Click to expand...

Handling in a vintage bike is not just one or two things -- it's a system with many interrelated parts. Your particular issue could have several different overlapping causes. You'll need to look at several different things to make improvements. At the moment, the stock shocks are the most obvious limitation in your bike's overall "system", barring mechanical issues. Until you fix that, changes to the front end will have little effect.

In terms of priorities, first make sure there are no mechanical issues, like bad swingarm or steering stem bearings. Make 110% sure you're starting with a stable, perfectly functioning frame. Do NOT assume anything and do NOT skip this step. Take the rear wheel and shocks off and check the motion of the swingarm carefully. Remove the swingarm pivot and grease the bearings. Upgrade the steering stem bearings to quality tapered bearings if that hasn't been done yet. Make sure everything is straight and there's no binding. Check the wheel and sprocket carrier bearings carefully.

Make sure the brakes front and rear are tip-top -- stock GS brakes work astonishingly well with fresh innards, pads, and stainless lines. Make sure your rear brake pivot isn't binding in the frame.

You've already done the springs in the front fork, which is where most start because they're relatively cheap and the positive effect is dramatic. It's a fantastic start, and it gets the front end 90% of the way there.

Next, upgrade the rear shocks. The stock shocks were junk 30 years ago and age hasn't improved them. Yes, I know some folks are saying this particular problem could be in the front, but I think they may be assuming you've already upgraded the rear, or that the shocks are functioning correctly. They are not. Until you fix this, you can dink around with the front all you want without making much difference in handling. In other words, you've already started by upgrading your front end, so the limit at the moment is the rear shocks. Upgrade these so you have a predictable platform. (the minimum is Progressive or Hagon shocks for around $220 - $250 a set; the Bitubos above are interesting, and there are several other brands such as Ikon.) Don't waste your time with the $80-$100 Chinesium shocks. Some have also installed slightly longer shocks to quicken steering.

Once the rear end is behaving, turn your attention back to the front end. Some 1100E owners disable the antidive crap, and lots of GS owners have installed Race Tech Gold Valves to improve our primitive damper rod forks.

Once that's done, then some people install a fork braces. This is sort of the last priority, and to a degree a fork brace is a matter of taste.
 
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I have been reading this for a while, biting my tongue. I think the most-obvious way to improve the situation is to PREVENT IT.
Rob S. said:
I have a tendency to go too fast on the streets (make a light, etc.), which necessitates having to slow almost to a stop rather quickly. My rear wheel hops, the whole bike shudders and I'm on the verge of losing control.
Click to expand...


If you KNOW that the situation exists when you ride like that, why keep aggravating it?

Yeah, you probably need to change the shocks and finish fine-tuning the front, but remember:

"An ounce of prevention is worth a pound of cure". :-\\\

.
 
Steve said:
I have been reading this for a while, biting my tongue. I think the most-obvious way to improve the situation is to PREVENT IT.


If you KNOW that the situation exists when you ride like that, why keep aggravating it?

Yeah, you probably need to change the shocks and finish fine-tuning the front, but remember:

"An ounce of prevention is worth a pound of cure". :-\\\

.
Click to expand...


I just hope he is going AGAT this time around. I have never felt anything like this on either my 750EX or 1100ED in any state of suspension.
 
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