19-07-12, 07:35 PM
When I changed my rear disc last year I had similar difficulties undoing the bolts. The screwlock Yamaha used on assembly seems to gain strength with time... I'd had minimal difficulty with the front discs, but have needed to change those every 3 or 4 years so the bolts hadn't had so much time to bond to the hub.
Cooking the rear wheel to about 50ºC softened the compound sufficiently on 4 of the bolts. The last two were really stubborn, I ended up taking U-channels of 3mm scrap steel with a 12mm hole near the end and welding them to the bolt heads. The higher temperature and extra torque I could apply was enough to shift them.
![[Image: reluctant_bolt.jpg]](http://i1139.photobucket.com/albums/n543/nerdybiker/reluctant_bolt.jpg)
I was a bit concerned that the high temperature could have weakened the alloy, but was able to torque the replacement bolts up OK without the threads stripping so figured that the heat that did reach the alloy was conducted away fast enough to avoid damage.
Cooking the rear wheel to about 50ºC softened the compound sufficiently on 4 of the bolts. The last two were really stubborn, I ended up taking U-channels of 3mm scrap steel with a 12mm hole near the end and welding them to the bolt heads. The higher temperature and extra torque I could apply was enough to shift them.
I was a bit concerned that the high temperature could have weakened the alloy, but was able to torque the replacement bolts up OK without the threads stripping so figured that the heat that did reach the alloy was conducted away fast enough to avoid damage.