In every brake thread I see everyone saying they wanted to move up to 7.5" from drum or 8.4" to 7.5" or vice versa. I know most say that moving up to 7.5" from 7.0" is a drastic change, but is anyone still using the 7.0" and find they are sufficient? I have just seen very few posts from people who are actually using them.

 

The 7" ones let you run 10" wheels, right? My car will only take 12" wheels (I have the later-model larger discs)...

 

you can run 10" wheels on 7.5" disks - I run 6 x 10

the 7" disks are just the very early ones .... first of the Coopers...1961

later the Cooper S brought the 7.5 which were considered to be a much improved brake

reference Mini Cooper and S, Jeremy Walton, speaking of the 998 Cooper (followed the original 997)

"The seven inch disc brakes are, admittedly, better than those fitted to early Coopers - they need to be - but they still provide remarkably little stopping for remarkably high pressure. So long as you don't overdo it, however, they will stop the car. But if you use 'em too much, too often, they fade right away."


The addition of a wider 10" wheel on the S allowed a larger disk area and the 7.5 disk with servo assist took the braking system to "excellent by the standards of the day..." There's discussion about why wider wheels allowed this larger disk is in the book .. mostly concerning air flow & cooling the disk; the metal mass to absorb heat increased significantly as did swept area. And the stock pad compound was changed.

So 7 inch might be OK but 7.5 is a significant improvement according to the reference and you knew that ... it appears the difference is in the performance once they get hot, plus the addition of the vac' assist in the 7.5 systems.

I've only driven on 7.5's tho . .

 

Looks like I'll need to keep my eyes open for 7.5" ones, then.

 

cuz you want to run on 10" wheels?

You said you have later/larger . . . many today want to run bigger wheels and if so there's no reason for smaller disks

 

They make a conversion kit to go from the 8.4" to the 7.5" to be able to use 10" wheels.

I was just looking for more support behind making the upgrade from the 7.0" to the 7.5" as it is ~$900, but I know I need to do it. I just had plans for that money already in my track Miata. Oh well.