Hi I have a 1985 90 and need to replace the front calipers and am getting confused as to which calipers I should use . Some suppliers supply Rtc3380 /3381 other state that these are not available and should be replaced with the latter one Rtc4498/4499 . I have found the earlier ones but they are expensive compared to the latter ones . Have looked through old threads and it's not clear if the later ones will bolt straight in .
Please advise
Thanks

Dunno..but consider rebuilding what you've got with lovely stainless steel pistons, cheaper and easy to do( with a little guidance).

I had exactly this.

The later ones are slightly bigger because they have bigger Pistons and take longer pads so there is more contact with the disc. Afaik they are the same as the calipers fitted to 110's

They will physically fit an early 90 but you will need to change a couple of other bits.

The metal brake line from the flexi into the caliper needs changing as the fluid I let is in a different place on the later calipers.

The master cylinder needs changing for the later one so it can cope with the extra fluid movement.

Now the master cylinder is a 'should be changed' type scenario - I didn't do this as I had only recently fitted a new oem one anyway. The result is the brake pedal has a small amount of travel before the brakes start to 'bite'. I was unsure about this so queried it with my mot place and they were happy. So upto you, but if your splitting the hydraulic system might be worth bunging in a new master cylinder to match.

Keep your old calipers - leave the Pistons in - and have them media blasted then rebuild them with stainless steel Pistons for the future. This is what I have done.

Also change your caliper bolts as they will knacker the heads coming out.

Feel your pain, I had exactly the same problem with my 1985 90". I bought a genuine caliper for £90 off ebay and a britpart one from Paddock, around £130. both work fine. my bores were scored and rusty. take yours off and split them. if the bores look OK, I'd rebuild and save a lot of money. if the rest of your brake system is as old, think about rebuilding the master cylinder and replacing the servo - the brakes on these old girls can be really good .