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G Tulloch

tyre too close to swing arm

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Hello all, I have an issue with one of my bikes.

I have 2 beta evo's. 1 is a 2015 250 and 2 is 2018 125.

The tyre on the 125 is very close to the swing arm on the brake disc side. On the 250 I can get my fingers in the gap but on the 125 I can't. Everything is the same on each bike checked measurements and cant see any difference. Snail cams are set the same on each side on the 125.

Checked measurement from centre of swing arm bolt to centre of axle bolt on 125 and it is even so don't know why the tyre is so close to the swing arm.

Any thoughts?

Look forward to hearing from you all

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The rim might not have the correct offset from the hub

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Are both wheel spacers the same size? If they are different they may have been put in the wrong way round - swap left with right?

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I have a Friday afternoon evo 2019 & one of the faults was the offset on the front wheel was way off, worth checking.

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I wouldn't go too much on where the snail-cams finish, they can be out by a couple of notches, as one side takes the weight of the chain and the other doesn't.

You could try two long straight-edges against each side of the rear tyre, to see if it is in line with the front wheel.

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Granted, I'm new to moto trials bikes, but I've been around trail bikes for many years, and I was a professional bicycle mechanic in college, so take what I say with a grain of salt, but I think it still applies.

As others said, it could be as simple as wheel spacers on the wrong side.

It could be your wheel dish, too. To check the dish (alignment of the rim relative to the hub) of your wheel, take the tire off and get a straight edge/ruler and place it across the rim, then measure to the wheel spacer.  Do that on both sides.  They should be the same (I think).  They're usually different on bicycles because of the gear cluster in the back, but I think most motos should be at least close to the same. If it looks like your wheel dish is off, start at the valve, and loosen all the spoke nipples on the side that's too close to the swing arm, each by a 1/4 turn.  Then tighten the other side by 1/4 turn.  Repeat until the rim is centered.  Then check if the rim is still straight, and tighten/loosen individual spokes accordingly to straighten it if needed.

It doesn't sound like you suspect frame damage, but a bent swing arm can cause this same symptom, too.

Also, how did you measure the distance from the swing arm pivot to the axle?  Often times the swing arms are shaped differently on each side.  Not sure you can just measure straight from one to the other because of that angle relative to the center line of the bike.  Maybe use a carpenter's speed square and use the right angle on it to measure off the pivot, so your tape measure is parallel to the center line of the bike.  Might not make a huge difference, but you never know...

 

The other thing to consider is, does the tire rub he swing arm?  If not, I'd leave it as is. 

 

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Just swap the wheels between bikes and see if that cures it then at least you know if it's the wheel.  If the spacers are in the wrong side the chain alignment would be out I would think?

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If they have the original wheels, both of those bike should have the latest EVO tubeless wheel with spokes laced into an central flange on the rim. The spacers for these wheels are identical and the disc should run about central in the caliper.

I have seen that the standard snail cams differed slightly in contour over the years, and as you have two bikes of different years, you could have one of one type and one of another type fitted to the same spindle -worth checking as a few mm on one side could make all the difference. If the alignment is out it will also cause the chain to try to come off the spockets and snag.

The other point is that the stop for the snail cams on earlier models was an aluminium lug part of the swinging arm which can get damaged and affect alignment, whereas later models had a socket head screw screwed into the swinging arm for the snail cam to notch onto.

If you are checking the alignment with string or a straight edge, remember to allow for half the difference in width of the front and rear tyres!

Hope this helps

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