Engineering type question

Rebel · Post by **Rebel** » Sat Jun 03, 17 6:59 pm

Is it possible and safe to have the internal diameter of a wheel rim machined larger?
Will it weaken the structural rigidity of the rim?
As can be seen ( hopefully ) in the pics below, my wheels have a "step" or taper on the inside of them, it makes the rim 1 inch narrower over the two inches of the rim closest to the centre hub.
This step or taper is preventing the wheel from fitting over my disc and caliper.

Garp · Post by **Garp** » Sat Jun 03, 17 7:58 pm

I'm not being a smart-arse, but you MUST have heard the expression " trying to redesign the wheel" before ?
I'd guess that there is a lot of maths in every wheel and I wouldn't mess with it - you could end up regretting it. I'm not sure they build-in "excess" on those rims. It wouldn't be cost effective to use more metal than they need.
It's all structural

Rebel · Post by **Rebel** » Sun Jun 04, 17 12:46 am

No worries, I know your not being a smart arse

Can't see any reason why it can't be done, always assuming it's even possible to do it or find someone willing and able to do it.
I suppose that what appears to be excess material might in reality be structural. They were made in the early '70s though and as technology has moved on, I thought it might be a possibility

Blue · Post by **Blue** » Sun Jun 04, 17 7:49 am

How thick is the rim at that point and how much would you need to remove?

charger01 · Post by **charger01** » Sun Jun 04, 17 8:46 am

What about spacers and longer studs Nige?

Rebel · Post by **Rebel** » Sun Jun 04, 17 10:20 am

Blue wrote:How thick is the rim at that point and how much would you need to remove?

Without taking the tyre off to check the profile of the rim underneath it, it's about an inch and three quarters thick at that point.
I'd need to remove an inch of material over a two inch width heading towards the centre hub of the wheel. If that makes sense.

Rebel · Post by **Rebel** » Sun Jun 04, 17 10:26 am

charger01 wrote:What about spacers and longer studs Nige?

Thought of that as well Ade, everywhere I've tried so far don't have any with a 71mm centre bore though. Although not perfect as a solution, admittedly it would be easier to use them

andyrob · Post by **andyrob** » Sun Jun 04, 17 10:54 am

take a tyre off and use some calipers to measure rim width, barrington metals could machine them, but to me sounds like the wrong route to go....
Ide be buying a set of wheels and sell yours

Faux-7-0 · Post by **Faux-7-0** » Sun Jun 04, 17 11:17 am

Alloy wheel technology has undoubtedly advanced but your wheel design reflects the characteristics of the alloy compounds available at the time. You can undoubtedly get the inner rim machined but I think you're asking for a fatigue failure further down the line if you do so I'd look for another option. Just my opinion though.

Pete · Post by **Pete** » Sun Jun 04, 17 12:16 pm

Imagine the difficult conversation with the Police and the Insurance company if the wheel failed after you machined it and there was an accident.

In my opinion, it is not worth trying to short-cut this sort of thing when primary safety factors are a consideration.

Rebel · Post by **Rebel** » Sun Jun 04, 17 1:59 pm

Thanks for all the replies and advice.
I was mainly just bouncing ideas around for a possible solution, did think that machining a rim itself sounded like a dodgy idea but with no machining experience or wheel construction / design knowledge with regards to fatigue and stress factors etc, the question had to asked.

Blue · Post by **Blue** » Sun Jun 04, 17 8:43 pm

It all depends how much you need to remove, if we are talking more than a 1/4" inch in total then no chance, 1/8" off the rims and 1/8" off the callipers will almost certainly be safe but I have a feeling we are talking a lot more than that. You need to measure it up carefully and I think it will be very obvious that no 15" rim will work. 16" might clear but the tyre selection will be poor so most would go to 17".

Rebel · Post by **Rebel** » Sun Jun 04, 17 9:34 pm

It would need an inch removing, based on not knowing the design of the rim under the tyre without removing it and not wanting to leave any wafer thin areas that could give me a nasty surprise or worse.

I did manage to try the disc and caliper on an appliance mag 5 spoke, it fitted perfectly with about three quarters of an inch clearance between the rim and caliper but the internal rim was all the same level. It's obviously a design feature of my wheels, to date I've never seen a wheel with a step on the internal rim.
So, all I need to do is find a pair of 15 inch rims with no step on the inside to use. In the meantime though, I've managed to borrow a pair of spacers for now.

Super Sloth · Post by **Super Sloth** » Sun Jun 04, 17 10:39 pm

If you can't get hold of a spacer, what about giving those universal ones a go for mock up? You can then get something machined up locally as a more permanent solution?

Another option might be to go up an inch in rim size?
This company does some nice stuff.

http://www.imagewheels.co.uk/billet-18-alloy-wheel/

Rebel · Post by **Rebel** » Sun Jun 04, 17 10:45 pm

I've sorted a pair for now, on long term loan. Means that I can get it MOTd and make sure everything is working properly while I search for the right wheels