Front tire cupping!

deputy_hood

I have a 91 ST1100. I noticed the front tire, which looks fairly new, is badly cupped on both sides. I also noticed if you release all pressure on the handle bars, they will start to shake back and forth violently. I'm not sure what would cause this. I know on a car cupping is usually caused by bad shocks, but I'm not sure on a bike. Any ideas would be helpful.
 
Last edited by a moderator:
The cupping is causing the shaking.

What is causing the cupping is more than likely your suspension setup.

If you are not 165 lbs, you are probably going to need to upgrade the suspension.

Search around a bit and you will find a tons of posts about springs for the front forks.
 
In addition to Rob's suggestion.
Low tire pressure and Jack rabbit starts too.
What do you use for your tire pressures?
I use 43/43.

Mark
 
Thanks for the help guys! I weigh 240, but the tire was cupped before I got it. I will check the pressure and adjust appropriately. If that doesn't work, I guess I will have to go on a diet.:hamburger
 
Loose steering head bearings may also be the culprit. When I lived in Bayfield, the Honda dealer in Durango (Handlebar) had a fairly competant crew of wrenches who sorted out a few things on my ST1100--if all else fails, let their service writer take it for a test ride and give you a prognosis. There's also an excellent gypsy mechanic (Steve Mooney) who has a shop out on 160 (east), across the road from the new Suzuki dealership.
 
I talked with a Metzler tire rep a couple of years ago and he said the best way to keep tires on a Wing from cupping was to run 44-46 pounds in them. I no longer have a cupping problem on either bike.
 
Soft front suspension (soft springs, needs new fork oil) makes the tyre do more work to make up, so it will cup (similar to your car experince). Front needs at least 36psi (depending on the brand and loaded weight of the bike) and probably more if the soft suspension is retained.
 
Unbelievable!:hat1:

Yep, bought mine with a cupped front tire too! PO was about 200 lbs but he only had the bike 1 year. Don't know about the PO before him. I only weigh 155 but boosted the tirre...(tirre? :rolleyes: ) tire pressure to what is max for the tire. Had some issues with tar snakes and road irregularities. Some bonehead (no not Bones!) ran into the front of her and almost knocked my new baby over in a parking lot and managed to push a fork seal over the edge. Had the stealer (insurance paid up for an inspection!:clap2: ) check her out, replace the fork seals and fluid, plus installed tapered roller bearings in the steering head. No more wandering with irregular road surfaces and the tire cupping has been brought to a stand still! I did not change my front springs. As others mention, change out that fork fluid (may as well change the seals too), install the taper bearings and keep up with your tire pressure for longer tire life!!!:-D
 
Tapered roller bearings in the steering head corrected the headshake on my '93 ST1100. Tire pressure seemed to affect cupping, or lack thereof. Mine was OK if I kept it up to spec.
 
Several people have said that tapered bearings stopped their head shake while others have said that it didn't help them. I would guess that the shake is caused by tire wear, tire pressure, bearings, fork oil and maybe some more things.

Since you say the tire is pretty new I would up the pressure to max for some miles. Then if the cupping is getting worse I would replace the tire. If the problem is still there I would try the fork springs and oil. As long as the front end is apart that much I would go for the tapered bearings as well. :03biker:
 
My front tires stopped cupping when I learned how to properly steer... It seems I was *holding* the bike down with my weight and pushing the wrong way on the bars... This was causing the bike to want to stand back up, but it couldn't because I was physically holding it down. The front tire's contact patch was not *even* on the road (and I did experience some loss of traction on the front from time to time)... YMMV...
:cool:
 
"Cupping" on a motorcycle tire it not the same as cupping on a car tire. It's not really cupping at all. And it has nothing to do with headshake or tire pressure.

Cupping on a motorcycle tire is simply the phenomenon of the individual tread blocks deforming under cornerering and/or braking forces. These forces actually bend the tread blocks a bit and then the wear becomes uneven as a result. To illustrate what's happening, take a wood pencil with a new eraser and hold the pencil, eraser down, on a flat surface. Fine sandpaper will illustrate this even better. Now, while continuing to hold the pencil perfectly vertical so that the flat end of the eraser is firmly against the sand paper or other surface, press down on the pencil and drag it in one direction. Now look at the end of the eraser. You'll note it's worn primarily on the leading edge. The same thing happens with the individual tread blocks on motorcycle tires. The smaller and more defined the tread blocks are, the more you'll see this phenomenon. The larger and less defined they are, the less you'll see it. It's perfectly normal. Yes, increasing pressure will reduce this effect somewhat because you make the whole tire that much stiffer. But remember that most motorcycle tires have an upper pressure limit and for most of the tires I'm aware of for the ST, that's 42 psi. And that's only to be used when the tire is carring it's maximum rated load. Also remember that you really don't want to be running those kinds of pressure if you want to have maximum traction available from your tires. Unless you're very heavily loaded, 36 in the front and 40 in the rear is plenty. Remember that smaller sport bikes run down into the mid 20's. Running more pressure in a motorcycle tire than is necessary does a number of things. One, it reduces the contact patch area with the road. Two, it make the tire harder and stiffer which reduces it's compliance so that it's ability to adapt and conform to the road surfaces is compromised, and it means the tire does not flex as much so that often, the tire never comes up to the proper designed operating temperature. Bottom line, 36 to 38 is fine for the front tire on all ST's. Cupping is normal. And if you're having headshake problems, there are other, much superior ways to solve them.

Cheers!
 
Yes, often you can prevent a tire from "cupping" by raising the tire pressure. But at the cost of a smaller contact patch, less compliant tire, and reduced maximum traction. Not a good trade off in my book, especially when you consider that a "cupped" motorcycle tire is still fine to ride on.
 
You must log in or register to reply here.
Back
Top Bottom