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Wheels and Tyres - 10" Wheel conversion issues

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Wheels and Tyres - 10" Wheel conversion issues

Postby TechTeamMod » Tue 9th Sep 2008, 08:54pm

10" Wheel conversion issues

The idea of this article is not to tell why to change to 10" or how to do the conversion both these topics are covered in great detail in other places. The purpose is to cover some of the major decisions that need to be made. This information may seem obvious to some but as a relative new comer to minis I would have appreciated information like this to help me make decisions.

Disclaimer: All views expressed below are the opinion of the author. This is not a technical guide but a collection of views and opinions I have gathered over the past year or so. Also I have not tested/used all these setups but I am using information from trusted sources for information, so please bare this in mind. Don't take this as gospel, if you don't understand ask or research the problem more fully yourself
Also before carrying out any work ask yourself if you are capable of doing the work safely, or if getting the work done by someone else would be a better idea. Brakes are very important and should not be looked at with the attitude of "it'll be-arite".

Brakes

The biggest decision to be made is which of the many type of brakes you will use that will fit under your 10s. When making your decision please remember that your brakes are potentially the most important part of you car and cheaping out here can be a false economy.

note: If you are currently on drums and are using this guide to help you choose a disc setup you will need disc hubs and CVs as the are different.

Drums

Most minis produced before 1984 used front drum brakes. These are a valid option for you if you want to run 10" wheels on a budget, as they are fairly easy to find for free as people upgrade their drum minis to disc brakes systems. Despite their reputation as rubbish I find mine perfectly fine for town driving. This said stopping from motorway speeds to a halt can be an experience as brake fade *can* come into play (possibly down to them being in a poor state of repair-turned out mine had 1 working rear piston!).

If your looking for a cheap way to convert to 10s and drive like a saint, then drums might be worth considering (but are not recommended especially if you are swapping down from 8.4" discs).

7" Discs

Used on early coopers to allow disc brakes to be fitted under the 10" wheels for the first time. These have a reputation as being worse than drums, so although an option are not recommended. Also these are fairly rare so will probably cost you an arm and a leg for the privilege.

7.5"Cooper S Discs

Used on later coopers (*not* the rover ones) and also on early 1275GTs these are the favourite brakes in 10" conversions. These brakes provide good braking power and due to their popularity are a product that can be trusted. The calliper where not fitted at production since the 70s so its fair to say they are pretty rare. There is a booming 2nd hand market for "S" brakes and some of the prices are almost comical in there magnitude (I have seen people asking £200+ for very rusty looking setups where you might be lucky to save 1 calliper).

If buying second hand always inspect the brakes as fully as possible looking for any damage or problems like seized pistons or knackered bolt heads. When taking this route a full refurb is highly recommended as most setups will be getting on for 30 years old! An alternative is to buy a conversion kit from a specialist, these will generally provide all you need to do the conversion with new or fully refurbished parts as appropriate (dependant on supplier). Minispares even stock a remanufactured part for about the £120 a calliper mark, great value for piece of mind in my opinion.

Alloy 4 Pots

These are now becoming more common on 10" wheeled minis where before they where mainly a racers item. There are now several manufactures of alloy calipers: minispares, minispeed, minisport and KAD all produce their own designs. They come in 2 flavours: ones that use 7.5" cooper S discs and flanges; ones which use 8.4" discs and flanges with the disc machined down (usually 7.9" but I have seen other sizes used, the calliper manufacturer will recommend what diameter this should be).

Either way these are a good option for people wanting more brake power or for those who don't trust refurb parts. One point to note though is that 4 pots tend to be larger so wheel clearance issues may be possible but the only way to tell really is to try and fit your chosen wheels!

Mk1/2 Ford Fiesta Conversion

This is a bit of a new kid on the block so is not as tried and tested as the above options. This is the cheapest way to get decent stopping power onto you mini and still fit under 10" wheels.
The down sides to this conversion is that you need to machine the hubs to accommodate the callipers (the holes need boring out slightly, and a face for the calliper is needed) as well as a slight modification to the calliper (small section of webbing needs removing. You will also need to source some metro drive flanges (which will need the wheel locating lugs removing), get some 8.4" discs machined down to 7.9" and get some custom hoses made up. The plus side is if you are confident enough to do the work (or know a man who can) then this is a very cheap solution (usually under £100 all in).

note: although mk2 fit they are a bit more work and may require spacers

Daft Spacers

OK they aren't brakes but they are going here anyway. It is possible to use HUGE spacers to get some wheels out far enough to clear a 8.4" calliper and disc, there is even 1 brand that will sell you a wheel with it built in. Thing is this strikes me as daft for 3 reasons: your wheel will stick out by about a yard; you will adversely affect the handling of the car; you also won't be doing your bearings any favours....yes it's dirt cheap, yes it sometimes works, but it's still a daft idea to try it so I don't know why I even mentioned it!

Wheels

There are loads of different wheels available in 10" with a 4" PCD (pitch circle diameter, this is the circle on which all you wheel stud holes are drilled). These range from the std steels (various types over the years from boggo 1980s steels to the desirable reverse cooper steels) to alloys (and loads some designed with drums in mind some for discs) to full race split rims.

Once you have chosen your wheel there is a chance it will foul on the callipers (mainly a problem on old steels and older alloys designed with drum brakes in mind, but will depend on your wheel and calliper choice). If this happens you only really have 3 options:
  • change your callipers...probably not going to happen unless you *must* have these wheels
  • change your wheels, more likely outcome
  • if they foul but only just then you can use a small spacer to get the clearance you need. Personally I would try keep the spacer under 1/2" as I have heard bad things about large spacers.

Another problem is now that your wheel diameter is different you will need to change you speedo drive gears so that your speedo reads correct(there is a tool in the downloads area to help you choose what you need)

note: Your final wheel/brake combo may cause the wheel to stick out from the body work, if this is the case you will need appropriate arches to cover them, its the law!

Hope this helps you make an informed decision, and alerts you to the possible pitfalls in making the decisions involved in making the swap.

Useful sources of info

  • Haynes manual - covers the basics of removal and re-fitting of the discs (they are after all essentially the same just different sizes)
  • Search the forum - there are loads of 10" wheel conversion threads in the forum (where I picked most of this up) they cover most the issues involved
  • also one of the mags covered physically doing the swap recently so get digging! (currently sept 05)

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