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Sullybiker · 05-04-2017, 09:34 AM

I have this on my TT250, it's actually always been there, but became greater in amplitude when the tyre wore down.

I thought I had a warped rotor that was grabbing, but when I lifted the front wheel I realised it was the tyre. It only happens between 35-40 mph.

First, check your rim is true. They're big clunky steel things and it's unlikely that it's gone out of true, but good to rule it out, right? Get some large zip ties, or anything you can fasten to the bike to make a crude pointer (a little screwdriver zip-tied on also works, but I use the pointy end of the ziptie itself) place the tip of your improvised pointer near the rim, not quite touching. Sight along the rim (I kneel at the front of the bike and sight in on the gap between the fork leg and the wheel, where I fix my ziptie) spin the wheel and you'll soon see any deviation from true (runout).

My rim was fine, it had a tiny bit of lateral runout (side wobble) and no radial runout (up and down wobble) that I could see at all. I placed a wooden block under the tyre, again not quite touching, (you can use a book, anything you can choose from various thicknesses) and could clearly see the front tyre was out of round as it spun above the block.

There's a rubber ridge on the tyre bead that runs around all the way around the tyre, and in my case it was clear that it was slightly higher at one point relative to the rim, as if the tyre was slighty big for the rim and it had bulged out at that point.

The tyre is nearly done anyway, so I'm leaving it for a few days. In the meantime I deflated the tyre, massaged the bead with my hand (ooh err!) and put a little tyre oil on there, I then inflated the tyre slowly to 1.5 times the recommended pressure (around 45-50 psi), Let it sit for a minute, then deflated the tyre to the correct pressure. This was to encourage the tyre to reseat, although if it has deformed (mine has) it will only do so much. It's helped and has reduced the wheel hop to what it was when the bike was new, I can live with it until I throw a new tyre on.

If you do some googling, you'll learn that inexpensive dual sport tyres tend to have quite iffy quality control, they're usually difficult to balance. I don't mind so much on a bike that rarely sees more than 50mph.

05-04-2017, 09:34 AM	#7
Sullybiker Join Date: Dec 2016 Location: Western PA Posts: 363	I have this on my TT250, it's actually always been there, but became greater in amplitude when the tyre wore down. I thought I had a warped rotor that was grabbing, but when I lifted the front wheel I realised it was the tyre. It only happens between 35-40 mph. First, check your rim is true. They're big clunky steel things and it's unlikely that it's gone out of true, but good to rule it out, right? Get some large zip ties, or anything you can fasten to the bike to make a crude pointer (a little screwdriver zip-tied on also works, but I use the pointy end of the ziptie itself) place the tip of your improvised pointer near the rim, not quite touching. Sight along the rim (I kneel at the front of the bike and sight in on the gap between the fork leg and the wheel, where I fix my ziptie) spin the wheel and you'll soon see any deviation from true (runout). My rim was fine, it had a tiny bit of lateral runout (side wobble) and no radial runout (up and down wobble) that I could see at all. I placed a wooden block under the tyre, again not quite touching, (you can use a book, anything you can choose from various thicknesses) and could clearly see the front tyre was out of round as it spun above the block. There's a rubber ridge on the tyre bead that runs around all the way around the tyre, and in my case it was clear that it was slightly higher at one point relative to the rim, as if the tyre was slighty big for the rim and it had bulged out at that point. The tyre is nearly done anyway, so I'm leaving it for a few days. In the meantime I deflated the tyre, massaged the bead with my hand (ooh err!) and put a little tyre oil on there, I then inflated the tyre slowly to 1.5 times the recommended pressure (around 45-50 psi), Let it sit for a minute, then deflated the tyre to the correct pressure. This was to encourage the tyre to reseat, although if it has deformed (mine has) it will only do so much. It's helped and has reduced the wheel hop to what it was when the bike was new, I can live with it until I throw a new tyre on. If you do some googling, you'll learn that inexpensive dual sport tyres tend to have quite iffy quality control, they're usually difficult to balance. I don't mind so much on a bike that rarely sees more than 50mph.
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