hi was hoping someone might be able to help me out with a question??
i've just bought a second hand pair of fox talas 32 forks really nice, but they are IS mount for the front disc and not post mount like on my currant forks which im using a avid 185 disc on, my question is do i need to use a 203mm disc with the IS adapter or will the 185mm with adapter still fit?
depends on the brakes but you can get IS to PM adapters that'll work for you I think.
Giant do an IS to PM adapter that doesn't rely on a bigger disk.
Pretty sure on my old bike, that a 185 Avid rotor worked with the fork as it was. It was an IS mount Judy with a Juicy brake and a ~180mm rotor (can't remember the specific Avid size - 180, 183 or 185).
That depends what size IS adaptor you have (I've just re-read your post a couple of times and can't see a mention of that). If you have a 203mm adaptor then yes, you will need to run a 203mm rotor. If you put the caliper on a 203mm adaptor and use a 185mm rotor, the caliper will sit too far from the fork leg and the pads will not meet the braking surface - kind of like putting a 26" wheel in a road bike and finding the brakes don't meet the rim.
If you want to continue using your 185mm rotor, then you'll need a 185mm IS adaptor, usually a cheaper option than buying a new rotor.
As to whether you need a 203mm rotor, it depends on your riding, how big you are and how powerful you want your front brake to be. I run a 180mm front rotor for XC and it's as much as I'd ever need.
thanks for the replies guys and so quick, but yes yr right relliott6879 that's indeed what id like to do, which is to continue using my existing 185mm rotor but with the IS adaptor that came in the kit which I have and don't have to buy another rotor which always makes me happy. 🙂
I only asked this question because id asked in a local bike shop if this size would fit to my new fork OK and was told that id probably have to use a larger rotor to compensate for the IS mount !!!
Which I have no doubt that he could have sold to me for a princely sum!!!
What a strange thing for your LBS to say! I ran a 180mm rotor on an IS mount on my old bike for years, on a Fox F80 RLT fork and before that a RockShox Judy 100. At the time of purchase, a 180mm rotor was considered large, with 160mm front and 140mm rear rotors being the norm. Post mounts were still a brainwave waiting to happen back then, so I've no idea why your LBS should say suggest that IS mounts require dinnerplate rotors. Unless, as you say, it was an attempt to steer you into a purchase.