16 replies to this topic

[ac427]

I was looking at Mk.4 Mini's but have come across a nice Mk.3 Mini.

 

Is there much advantage to having a single bolt subframe over the original 2 bolt front subframe for road and track usage?

 

Are there any other differences between front subframes types on manual transmission cars, during the Mini's production run?

 

[Ethel]

I think we'd all prefer the "2 bolt" Mk 3.

 

It's bolted directly to the shell, without rubber mountings, which makes the handing that bit sharper. It also means there's no rubber bonding to fail & the floor mountings are in a better place that doesn't cause fatigue cracks in the toe board.

 

General condition matters more though.

[ac427]

I think we'd all prefer the "2 bolt" Mk 3.

 

It's bolted directly to the shell, without rubber mountings, which makes the handing that bit sharper. It also means there's no rubber bonding to fail & the floor mountings are in a better place that doesn't cause fatigue cracks in the toe board.

 

General condition matters more though.

 

Thank You Ethel. 

[Icey]

It’s way….way down the list of things to be concerned about on a Mini.

Our 80s shell has been solid mounted on a single bolt subframe for 10+ years of road and track driving, no issues.

[mab01uk]

 

I was looking at Mk.4 Mini's but have come across a nice Mk.3 Mini.

 

Is there much advantage to having a single bolt subframe over the original 2 bolt front subframe for road and track usage?

 

Are there any other differences between front subframes types on manual transmission cars, during the Mini's production run?

 

 

The later subframe was rubber mounted to reduce noise and increase refinement but as said the downside is the handing/steering is less 'sharp' and gets worse over time as the rubber mounting parts age and in worse case fail. Several threads on TMF detail peoples experiences with replacing all or some of the rubber mounts with solid mounts. Some also say the later rubber mounted subframe when 'solid mounted' is harsher than the early solid mounted subframe.

 

Other front subframe differences were the engine mount holes on 1990's Minis were moved forward about 1/2" (13mm) and a longer top engine steady was fitted to give more clearance space behind the engine.

Edited by mab01uk, 24 November 2023 - 08:17 PM.

[ac427]

 

 

I was looking at Mk.4 Mini's but have come across a nice Mk.3 Mini.

 

Is there much advantage to having a single bolt subframe over the original 2 bolt front subframe for road and track usage?

 

Are there any other differences between front subframes types on manual transmission cars, during the Mini's production run?

 

 

The later subframe was rubber mounted to reduce noise and increase refinement but as said the downside is the handing/steering is less 'sharp' and gets worse over time as the rubber mounting parts age and in worse case fail. Several threads on TMF detail peoples experiences with replacing all or some of the rubber mounts with solid mounts. Some also say the later rubber mounted subframe when 'solid mounted' is harsher than the early solid mounted subframe.

 

Other front subframe differences were the engine mount holes on 1990's Minis were moved forward about 1/2" (13mm) and a longer top engine steady was fitted to give more clearance space behind the engine.

 

Thanks, It seems strange a solidly mounted single bolt subframe would be harsher then the solidly mounted 2 bolt subframe. Assuming the rigidity would be similar if not the same.

[GraemeC]

I’d agree - don’t see how it can be any harsher.

However what it can do is crack around the toe board mounts as both bolts are in the same flat plane.
Whereas the earlier one was bolted into two planes at the toe board and floor, with a nice stiffening fold in between them.

[Gaz66]

Given the choice 2 bolt every time 👍

[ac427]

I’d agree - don’t see how it can be any harsher.

However what it can do is crack around the toe board mounts as both bolts are in the same flat plane.
Whereas the earlier one was bolted into two planes at the toe board and floor, with a nice stiffening fold in between them.

Thanks GraemeC. I don't suppose anyone makes a 1 bolt front subframe that can bolt in two different planes?

Is there much work needed to make a 2 bolt front subframe fit a Mk.4 bulkhead?

[Ethel]

I too have wondered why nobody has made a bolt on extension to convert a mk4 into a mk3 subby. S'pose it'd take a bit more than just the mk4 subby mounting bolt holes with the added leverage. 

[coopertaz]

you could always make up some extension plates to go from lower subframe mounts to mount under floor if that bothered about cracking toe board obviously would need solid mounts too inplace of rubber or nylon.

[GraemeC]

I too have wondered why nobody has made a bolt on extension to convert a mk4 into a mk3 subby. S'pose it'd take a bit more than just the mk4 subby mounting bolt holes with the added leverage. 

 

Me too - would just need the solid mounts to be made longer and with a bend so they lapped under the floor.

I did once suggest this to MiniSpares but the thought was there wouldn't be enough call for them.  If I had more time I'd have a go myself.

[GraemeC]

 

Is there much work needed to make a 2 bolt front subframe fit a Mk.4 bulkhead?

 

 

The earlier bulkhead has a different internal strengthening arrangement to suit the 2 bolts rather than one, and because it is inside the bulkhead it would be difficult to do without fairly major surgery.

That said, I have had a car that had the earlier subframe in a later shell and they'd just drilled the holes and bolted it in - never noticed an adverse effects from that.

[Ethel]

I think it's more accessible than it appears: via the openings for the pedals & master cylinders.

 

I for one have never looked properly at the dimensions. The subframe towers look essentially the same & they house the same cones, trumpets & upper arms, which suggests the body is raised by the thickness of the rubber lozenge shaped jobby twixt subby & shell. We used to use cheaper front panels by drilling the holes for alternative front mountings & packing the gap with washers. It's been ages, but I can't recall using a Mk4 mtg as a guide so that was likely also a lozenge thickness lower???

[GraemeC]

I think it's more accessible than it appears: via the openings for the pedals & master cylinders.

 

I for one have never looked properly at the dimensions. The subframe towers look essentially the same & they house the same cones, trumpets & upper arms, which suggests the body is raised by the thickness of the rubber lozenge shaped jobby twixt subby & shell. We used to use cheaper front panels by drilling the holes for alternative front mountings & packing the gap with washers. It's been ages, but I can't recall using a Mk4 mtg as a guide so that was likely also a lozenge thickness lower???

 

Yes, you can access the bulkhead through those holes, but I wouldn't like to remove and reweld the strengthening through them!

If I remember rightly the dry subframes are the same height, the wet ones were taller.  A 2 bolt dry subby needed a 1/4" solid packer on top of the towers, which as you say will be similar to the rubber mount (or thick washer used in solid mounting kits).