I'm trying to work out of a big tyre will work with a HS33 brake booster
I need the length of dimension A in this pic
[img] 
[/img]
anyone ?
what boosters are you talking about? I've got evo2's and the boosters. aren't like that - going from the frame forward: there's a backplate that holds the setup rigid onto the mounts, then the brakes, then a 'mini' booster with a minimum of adjustability.
That said, from the top nut / bolt you've 5.6cm. That's NOT from the v-brake mounts but from the top bolt on the brakes themselves. The distance from mount to top of A is approx 10.4cm
There's a fair bit of space in there.
Hope this helps.
cheers for that. Yes the booster I'm on about is the one that bolts across the top of the two brake piston units. As you say, it's a mini booster - it doesn't connect to the frame bosses.
The standard ones look like this, but there are a few variants, which may be taller/lower
[img] 
[/img]
OK - mine look like:
[img] 
[/img]
The 5.4cm measurement given is from the top bolt upwards
ask on trials-forum
that's the one woffle, cheers