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Bush availability is pretty much the same story as the tie-rods, as is regular inspection/replacement. Something to remember here – do not do the bottom arm pin-retaining nut up tight until the car is placed down on the ground. If tightened when the cars up in the air, the bush can be twisted out of shape once on it’s wheels causing premature deterioration and possibly ‘squeaking’.
Adjustable bottom arms.
As we’re looking at doing this suspension-prep on a sensible budget, I’m keeping the choice down to the widely used, off-the-shelf types. There are a number of excellent alternatives, but are considerably more expensive. The choice is of two, and there’s not much between them. Originally, and for the longest time, rod-end facility was applied by cutting the inner bush-mounting bore off then welding on a threaded tube at a certain angle into which the rod-end screwed. No problem providing the welding was of a high standard. However, Mini Spares continual search for the best products at the price saw them re-designing the adjustable bottom arm by making them one-piece forged. Although the welded-on variety was reasonably trouble-free, with few reported failures, the one-piece forged items were seen as a way of eliminating the possibility of failure and consequently limiting ‘public liability’ insurance claims! For ultimate strength and weight reduction in a generally over-engineered component, these have to be the way to go. The only real problem with either of these styles is the inner locating pin has to be removed to facilitate adjustment, which means jacking the car up each time. Time consuming and unsettles the car suspension each time, making set-up a lengthy process. A number of the previously hinted at alternatives allow adjustment without doing this - but at severe cost.
Much discourse over the suitability of rod-ends on road/high-mileage cars has been ‘enjoyed’; the main issues are longevity and noise transmission. So for the record – the myriad of rod-ends available allows a suitable one to be chosen for its given environment. Those supplied as standard fitment to Mini Spares/Mania ‘off-the-shelf’ suspension components tend to be a budget grade, suitable for a year’s tarmac racing - around 500 competitive miles. Fitment of extreme quality rod-ends would make them un-competitive in the market place. Using higher-grade items will give you decent life - so Mini Spares/Mania now offer the forged one-piece arms without joints for those that wish to source their own. Extra transmitted noise? You won’t notice it, and is imperative for maximising handling – and that’s what we want.
Tracking
Track is altered by the rod-ends screwed on to the steering rack track rods, the standard ones being generally well up to the task. The only consideration would be on severely lowered cars or on cars having extreme negative camber where the rod-ends are only held on to the track rods by a few threads. These will need either replacing with ‘longer’ ones, or a suitable full nut welding on to the standard ones – both to increase thread engagement. Triumph Spitfire items are usually used for the former, available from Mini Spares/Mania. I favour the latter as the replacement rod ends are only a few threads longer than the Mini ones. Welding a nut on doubles this extra engagement. If the latter route is used, make sure the nut and rod-end are screwed on to a track rod, but not pinched up together. The threads need to be ‘in line’ and spaced to allow the unit to be screwed on and off of the track rod easily without damaging the threads. You obviously need to retain the lock nut. A good tip here is to bore a 3/4 nut out using a 1/2 drill bit, sliding it on to the track rod so its about half way along it, then welding it to the track rod. Gives you a good area to use for adjusting track instead of wrestling about using either Vise-grips or an adjustable pump wrench!
Rear end
Here we’re only concerned with camber and track, both of which are generally/more easily adjusted using the same component – the outer radius arm bracket. In contrast to the front, track is the most important factor of the two; acutely altering how the car handles and its over-all stability so should attract the largest input of time and money. Whilst too much (or more than recommended) toe-in will have no real side effects other than increased/unnecessary drag and tyre wear on the outer edges, toe-out makes for attention-grabbing performance. A little toe-out makes the car skittish with a sharp turn-in/over-steer (back end trying to over-take the front), a lot makes it completely un-ruley in any other mode than flat-out, with severe over-steer at the slightest hint of steering input. And you just dont ant to get involved with what happens when lifting off mid-corner! Definitely not for the in-experienced, faint hearted or those of a nervous disposition.
Rear camber
Camber on the rear is used to fine-tune handling. Negative camber is used to increase rear-end grip when cornering, this can increase under-steer if the front end isnt adjusted to counter this. Positive camber the direct opposite. Neither have the severity of track variation though. There is a train of thought - indeed some positive proof in theory - that adding negative camber will increase roll stiffness. By only a very small amount - but there nonetheless.
Track adjustment is a 50/50 deal – toe-in is easy to correct, toe out very difficult unless brackets with track adjustment facility are used. More on these later – we’ll consider the fixed-track types encompassing the standard item, fixed negative camber type and adjustable camber type. All these can be easily adjusted to remove toe-in or add toe-out. Reducing toe-in is by the simple expedience of fitting shims between bracket and subframe, elongating the bracket to subframe mounting holes situated on the underside of the bracket. Ridding the car of toe-out entails elongating the inner radius arm pivot shaft hole towards the rear of the car. A right pain as this alters ride height (raising it) at the same time and is an arduous job. Once the correct track has been reached by doing this - it is really necessary to make a key that fills in the hole left by the pin movement to stop it returning there at an unexpected moment.
It is for the above mentioned reasons that the Mini Spares/Mania rear brackets are manufactured to ensure, as often as possible, that they give a toe-in setting on a vast majority of subframes. Far easier to sort that a chunk of toe-out!
Camber adjustment is made by moving the radius arm pivot shaft outer end up or down. Unlike the front, this adjustment is unlikely to alter the track. The standard bracket can be filed up or down to suit, and then a key fitted to maintain position once the right setting has been reached. Fiddly and very time consuming/frustrating. The fixed negative camber brackets available are supposed to alter camber settings by 1.5degrees negative. I’m afraid I can’t see the point in using these as they will only add this amount to whatever your standard existing settings are – these likely to be neither desirable nor even from side to side to start with. But then for those who do not have access to geometry re-alignment equipment, it may be the only option. This leaves the adjustable camber brackets – and is what is most recommended in this trio as you attain desirable settings that are exact each side.
Nirvana has to be track and camber adjustable brackets. There are a few styles on the market; all deal with adjustment to the pivot shaft outer end only. To decide which you prefer you need to consider functionality. THE most important point is the settings you use should not alter unless you want to alter them. This implies decent/fixed mechanical location then acuteness of adjustment, the finer increments available the more accurate the settings achievable. Once again, the Mini Spares/Mania offerings are manufactured with these criteria in mind. The others available simply dont meet the criteria.
Summary
For road-used racers - heavy-duty adjustable bush-type tie-rods, fixed negative camber bottom arms, and adjustable rear camber brackets are the best compromise/deal. For a little further investment, the adjustable rear camber/track brackets give a nice edge. Budget allowing – you can’t beat fully adjustable suspension with rod-ends on the front – road or race. Definitely worth the investment – and will get you more performance on the road than an equal amount spent on the engine. Maximum adjustability and location make rod-ended components a must on race cars.
Posted: Feb 02, 2005 12:54 PM