Posted this before but Keith Calver gives some useful advice on 13" wheels on the Minispares blog pages.....
Wheels & Tyres - Bigger wheel fitment considerations
By Keith Calver
"The 13-inch wheel/tyre combination brings out the worst in everything Mini suspension and brakes orientated - but to many the aesthetics far out-weigh all other considerations. And there are many considerations. Those who believe they are fitting this combination for increased grip and handling capability on a road car need to think again. Most of the 13-inch tyres are manufactured for heavier cars. This means a harder tyre compound is used. A Mini simply doesn't get the tyre up to its proper operating temperature, so the increase in grip originally hoped for doesn't materialize or isn't maximised. Wayward handling (unless suitable suspension set-up has been applied), heavy wayward steering, and exaggerated bump-steer are further consequences. These are caused by the offsets employed, necessary to get suspension clearance. 13-inchers are generally wider than standard rims, so the wheels are made with the greater portion of the extra width applied to the outside of the wheel, effectively pushing the wheel further out away from the car. This causes a greater leverage to be applied to the already poor bump-steer geometry of the Mini. The wider tyre needs different geometry settings to ensure the full footprint is road-surface bound as the lower, stiffer side-wall does not distort as easily as the 10-inch tyre types. Excessive camber - positive or negative - will cause the tyre to loose contact with the road surface when cornering or with extreme steering in-puts. This then causes the tyre to follow any deviations in road surface. The offset dimensions employed can also mean wheel spacer shims are required in certain combinations to gain clearance, and even the steering rack may need replacing with the one used on the Sportpack cars - and these are definitely not cheap, costing in excess of £100. These have built in lock-stops to reduce the turning circle to prevent the tyre scrubbing the inside of the rear of the inner front arch. Again, the types and styles are legion, so doing a comprehensive and accurate whose needs what is impossible in a few pages. The increased footprint increases drag - responsible for reduced top speed, reduced acceleration, increased fuel consumption (all neatly illustrated by the difference in performance figures between the Sportpack cars and the 12-inch shod variants, the 13-inchers suffering 6mph slower top speed and 0.6 seconds slower 0-60 with less mpg). This larger footprint-induced grip/drag increase will help with braking, but only if the brakes are equal to the task. The wheel diameter also gives a greater ('longer') leverage working against the brakes. The combined larger footprint and greater leverage means fitting 13-inchers to a drum-braked Mini is an absolute no-no. They simply over-come the applied friction capability of the shoes. Disc brakes are a must. Even the 7.5-inch S type discs are a little marginal in my opinion/experience unless steps are taken to maximise their performance envelope. The 13-inch combination is a good deal heavier in most instances than the standard set-up so up-rated dampers are an absolute must. Having considered, dismissed or navigated round the aforementioned problems and are still serious about fitting 13-inchers, one thing is certain - body surgery will be necessary."
Edited by mab01uk, 05 August 2016 - 07:58 PM.
bored of looking at 10s, plus still feels good to drive on. Won't be changing them any time soon
