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MG MGB Technical - wire wheel and bumper conversion

Like to hear from anyone who has done a rubber to chrome bumper conversion. I saw some that required body work to complete the look. I also saw that the wire wheel conversion is not to hard but i am confused about what adapter fits what wire wheel as i hear there is a different spline set up on some. Any advice on subject? thanks ,Doug
dd doug46chief

The later Salisbury/tube-type axle wire-wheel and stud wheel hubs are fully interchangeable on the half-shaft splines. However the wire wheel axle is narrower because of the different offset of the wheels, and putting those hubs on a stud wheel axle will put the tyres too close to the arches. There are so-called conversion hubs that bring the wheels in a bit, but even with those mine rubbed badly. Eventually I fitted a proper wire wheel axle - which needs a different handbrake cable.

The fronts are just a straight swap from one standard hub to the other.
PaulH Solihull

Hi Doug, I also have considered the bumper conversion (77 roadster) - spent alot of time researching how it's done etc - after alot of time thinking decided not go down that road. It looks easy on the net but there is alot of work beside the just putting on the bumpers and grill - respray around the new bumper supports, lowering the car and all the rest. And having seen a few bumper conversion results the cars look a fraction too short and stumpy - the proportions look a bit wrong. Of course up to the indvidual...respect for that.

I had to replace the suspension all round so I opted for 1 inch lowering kit and stiffer(30%)Armstrong dampers/springs at the front. I think it now sits better and not so much roll in the corners.

At this stage I am spending the time and money getting the car in good mechanical order and doing all the stuff the PO did not do... (by the way Paul got the half axle out using the bolt and nut behind the hub method - worked without out any problem at all)
/Moss
Moss

Tell you the other aesthetic point that can make the chrome bumper models look so good; The elimination of the chrome over-rider! I know the purists would baulk, but it looks so clean. Mike
J.M. Doust

Doug

The spline difference is the 12tpi and 8tpi which is just coarse and fine thread for the spinners.
12tpi is for cars up to 65 then 8tpi after.
Either can be put on either car.
The rear adaptors are specially made to compensate for the steel wheel axle but if you axle is already ofset to the left it will make it worse and start rubbing.
Check you gap between tyre and arch to see how far out of centre it is first.

Ste
Ste Brown

"The rear adaptors are specially made to compensate for the steel wheel axle"

Only a small amount of the excess in my experience, I had to replace the axle in the end.
PaulH Solihull

The conversion works out that it will be about 7mm wider than a wire wheel axle so thats why they only recommend that 165 and poss 175 can be fit.If you want to fit 185 it says change the whole axle for a wire wheel version.
This can be ignored if your body sits higher than the tyre with the new rear springs as the arch of the spring is wrong so will not catch as its not near the arch anyway.

Ste

Ste Brown

I have grown fond of the looks of my rubber bumper cars over the years. Although I own both types, my rubber bumper car is more "user friendly" on our roads due to its slightly increased ground clearance. The 68 scraped its center muffler on speed bumps to the point I had it removed. But, unless I was driving very slowly and carefully, there was a good chance of the chassis hitting the speed bump. The car looks good with the rubber bumpers (IMHO) but, when switching over to chrome bumpers looks too high unless the ride height is lowered, resulting in the problems I have with my CB car. The 68 is best of smooth roads while the 79 handles almost any road without problems.

As to wire wheels, I have replaced them on my 68 and my daughter's 77 with disc wheels. I have owned five British sports cars having wire wheels--a 53 A-H 100, two MGAs and two MGBs. I find the wheels excessively heavy (as compared to steel disc wheels and the MiniLite replicas available), which results in more unsprung weight and slightly reduced handling qualities. Add in the greater flex of the wire spokes, as compared to disc wheels, when cornering hard and the replacement of wire wheels with disc type make for a significant handling improvement. Add in the fact that I have seen numerous problems with wire wheels, even when used and maintained by people who are competent and enthusiasts, and the problems with spline wear on both the wheel hub and the axle hub, and I do not consider wire wheels to be desirable on anything except a show only car.

Les
Les Bengtson

7mm maybe, but the wire-wheel axle is 1.5" narrower than the stud wheel so you would need 20mm to put it right.

I had 165s with the conversion hubs on a stud-wheel axle. It was the axle offset that caused the problem, having less clearance on the left it rubbed on left-hand corners from the outset even with one-up and no luggage. Two-up and fully laden it was awful, I had to crawl round corners. First step was to fit RB springs, which stopped the rubbing and the grounding by increasing the ride height, but gave a very unpleasant ride over some surfaces. Then to wire-wheel axle and correct springs, which stopped the rubbing but left the bottoming and grounding, extending the shackles was needed for that. I've recently had to replace the tyres with 175s, and it's back to rubbing again occasionally.
PaulH Solihull

Paul
If you look at the picture 13mm is taken up on each of the conversion hubs.

Ste
Ste Brown

If the Rubber Bumper was created for anything it was for driving in London or New York. The rubber bumper has saved me serious damage on three occasions. Les also makes very good points about wire wheels (real pain and IMHO out of character) and the lower ride height (expensive in mufflers) doesn't do much more than the right bushes for roadholding. If knock-ons were important, I would go for the same German-made Dunlops as were fitted to the Twincam A.
Doug, the bodywork can be done with a conversion kit or rebuilt to match the original CB. The latter is a bit more work - both need a range of skills - and the brightwork !
Roger
R Walker

I have both chrome and rubber cars. The wire wheels are a pain and have been replaced with a new set of chrome wire wheel that after a few years are starting to get small areas of rust. The rubber car draws a lot of lookers as it is pearl blue on black and the bars are painted the same. It realy changes the appearance. Colour coding the bars might be worth a try before the large expense of converting to chrome. Ken
K Stuckey

Ste - you need 1.5" in total i.e. 20mm each side to keep the same distance between outer walls of the tyres. Believe me, I had severe rubbing after doing the conversion when changing nothing else, which went when I changed to the proper axle. YMMV.

I've had chrome wires on my CB roadster for over 20 years of UK weather, most miles of which have been on organised runs and many of those being wet, and a couple of salt. There are a couple of small rust patches on the hubs, which developed before I started spraying the rims and hubs with WD40 at the onset of each winter. I debated long and hard before plumping for them as they were by far the single most expensive part of the refurb. They do take an hour a wheel for a full clean, which they get 2 or 3 times a year. But against the Black Tulip they look absolutely superb and is well worth it. Each to their own.
PaulH Solihull

Paul

Like i said 13mm is compensated for by the new hub as in the picture on each side which only leaves 7mm to find on each side for your 20mm.
I do not know the offset between the wire wheel and the steel wheel so maybe the 7mm is compensated by that.
I remember the old hub conversions had a slim nut on the end of the studs years ago and now it is slim bolts through the drum.
Maybe they have altered something since you had yours on as you dont seem to hear people complaining about rubbing as much as we used to.

Ste
Ste Brown

I had slim bolts as you show, fat nuts now with the pukka axle.
PaulH Solihull

WOW, THANKS for all the help. Looks like the steel wheels will have to do. I have built indian m/c 's for yrs and I built them to ride not trailer queen them. So that being said I will drive this car and get the mechanics working well and enjoy it. thanks to all, DOUG
dd doug46chief

K Stuckey. Could you post of photo of your RB MG. Sounds neat.
Robert McCoy

Hi Robert I just realised I do not have any photos. I will take some but not for a while as the motor is pulled apart and it is raining here. If you can give me your e-mail address will send them later. Ken
K Stuckey

Doug
FWIW I have 15x5.5 72 spoke Dunlop chrome wires on my '77 GTV8 conversion. Had rubbing on the left wheel arch with 195 tyres but changed to 185 tyres and all's well (disc wheel axle with conversion hubs).
The car has been lowered to chrome bumper ride height.
I must say that I had to grind a couple of millimetres off the left hand wheel arch lip to eliminate the odd scrape on really hard cornering.
As others have stated - there is not a lot of room to play with using larger tyres.
Peter

PS. I must take issue with my fellow Aussie, Mike Doust - please put your overiders back on.
Peter Malkin

Oops Peter, at present I have no bumpers at all on the car! Looks really neat! But any minute our boys in blue might pull me up. To be honest I spent more time tinkering with it than driving the car, It's what I do, what I enjoy. If I persue the hill climb course, I may even trailer it to events, (with no bumbers!)As Paul said, each to their own. Incidentally Peter, I bought this car from a chap called Dave, in Melbourne. Kind regards, Mike
J.M. Doust

Could not help following this thread convert/ not convert - here's a pic of my RB with colour coded bumpers to match paintwork - no the colour is not original for the year(77) but was used in 79/80 - pewter metalic grey.
/Moss

Moss

"I may even trailer it to events, (with no bumbers!)"

Not homophobic, are you?

http://www.gccg.org.uk/
PaulH Solihull

Moss, that is a very attractive paint job. The rubber bumpers look much better painted. Sort of makes everything flow together. Well done.
Robert McCoy

This thread was discussed between 28/01/2012 and 10/02/2012

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