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Rallye Steels and Tyres - All you need to know!

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  • Rallye Steels and Tyres - All you need to know!

    This article was written by a colleague of mine who is one of the top Tyre and Wheel Engineers in the country - and is very useful.

    Please remember he is only going on the info I have given him - as he is not a rallye owner or enthusiast, but a wheel and tyre expert.

    Also there are some gaps where I have not been able to give him the info (one being off-set measurements), so I will change these at a later date.

    Enjoy!!


    1) wheel construction/size/strenghs etc.

    Series 1: 5.5JX14 H2 ET?? (NEED TO ADD IN WHEEL OFFSET VALUE HERE)
    Fabricated Steel (assume 5 stage disc forming operation using 5+tonne presses. Rim is cold-worked sheet, rim rolled to form and seam welded.)
    Assume 4 position tig welded disc-to-rim internally at wheel well
    Multi-stage pre-treatment (corrosion resistance equiv. of zinc coating) with white powder coat. Unlikely to be a primer, although could be powder coat black with white coat added to A-face only. Oven stoved paint curing.

    Wheel strength based upon wheel load requirements. Vehicle max axle GVW (divde by two) gives max wheel load. Steel wheel inherently performs well on rim impact testing, giving good kerb strike resistance, pot-hole damage is reduced etc. The impact performance vs. alloy is further increased given the fact that most vehicle manufacturers fit much larger dia. allow wheels.

    Corrosion tends to be bigger problem and paint chips easily, exposing ferrous metal, especially where no wheel trim is fitted(!) With aging wheels, weld integrity is worth inspecting, as is the land area under the bolt seat, where fatigue cracks can form. Cracks do not necessarily propagate, but this is still not a desirable condition.

    Steel wheels rarely have pressure leak problems (whereas Alloy wheel can have porosity issues), so once it passed the pressure test @ manufacturer, they rarely leak in the market.
    6JX14 H2 ET.... (OFFSET..?) Same as 5.5J, but with wider rim. This wheel will appear ‘deeper dished’ as the disc will be more inset inside the rim, to achieve the same wheel offset value.


    2) What characteristics of steels over alloys etc
    See text above.
    also: Steel wheels can be easier to balance (not necessarily on new assemblies where the alloy is more accurately machined) but in service where wheels have had impacts and thus produce rotational imperfections.
    Cast alloy wheels (pretty much 99% of all alloys are cast- forged are expensive but ligher & more balanced with linear grain flow... etc, detail not required) can have variations in the material masses as different areas of the wheel can cool at different rates, thus giving potential balance imperfections. Again, this is extentiated by the use of larger diameters; plus most stylists prefer the use of internal balance weights, thus requiring more weight to balance the assembly (this is further hindered by the removal of lead from balance weights as of July 2005 on new vehicles, so larger less dense zinc weight are now used). Steel wheels are pretty much all externally balanced (inner & outer rim) so the balance is easier to achieve.
    Size for size, you need to really be going over 16” to really see a difference in component weight. Most 15” steel wheels will be around 8, 8.5kg, where as an alloy may be (at best) 7-7.5kg. But as style adds weight (soft rim- not externally balanced, variation in spoke deisgn etc..) the average 15” alloy is probably very close to the steel. At 16” plus, the difference will be more. It’s unlikely that you will find a 17” steel in cars, unless there is a specific requirement.


    3) Widths 5.5/6 j how they compare and matter
    See top text for constructional difference.
    As for reasons/benefits: The 6J rim will effectively ‘stretch’ the tyre. This will have the effect of stiffening the tyre sidewall, potentially giving a quicker turn-in response as the load build up will be faster. The vehicle may feel more responsive overall and less ‘wallowy’ (sorry, there is no technical word to describe it). Ride quality may be reduced as impact resistance will possibly be worse. Depending on how the chassis is set-up, it may make the car more stable but twitchy, rather than softer but more predictable. 106 Ralle has tendancy to snap into oversteer (common with modified FWD chassis, especially where large rear ARB- anit roll bar, is used as load transfer occurs quicly at the limit) and a stiffer tyre can make this situation worse once mechanical grip is lost.

    4) what tyres are best for what (track use or normal driving)
    Everything mentioned above van be dramatically effected by tyre choice. Do not expect the car to handle the same with Chinding remolds or cheap budget tyres, as it did with the original OE approved tyre. Hundreds of thousands of pounds are spend to develop a tyre and match it with the vehicle chassis characteristics. Right from tread pattern selection, to tyre construction (number of plys, angle of ply tension, undertread rubber stiffness, sidewall apex position & stiffness etc..), through to dictating the tyre pressures.
    To just fit any tyre and expect it to work as the original did is wrong. Although saying that, many drivers may not notice the difference if the school runis the only demanding journey. It’s at the limit or in demanding conditions where the differences will be noticable. Wet grip, dry grip, cornering speed, ride comfort, tyre wear, tyre noise, vibration are all characteristics that can be modifed during tyre development; and all are linked. Simple example- you cannot have a tyre with excellent ride comfort that also has good grip levels. And vice versa.
    Effectively, to increase grip levels you end up with a stiff construction tyre, coupled with an appropriate tyre compound. This does not mean you want the stickiest compound around; you may achieve good dry grip levels, but its the construction which improves the cornering speed, the tyre response & feel etc., and to a certain extent the wet grip, along with the tread pattern design (something else that requires extensive research & development). And for fast road use, you want a tyre with good overall characteristics which will grip well in all conditions. Track tyres can be more biased towards high dry grip levels and can be thrown away and replaced after a race. this area is less concerned about working in a variety of conditions & terrains, and a sticky compound will generally do well, provided the construction is stiff enough.

    5) about tyres - tyre walls, widths profiles etc
    Tyre dimensions. I.E: 175/60R4.
    175 = tyre width in mm(external width from extends of sidewall) This is nominal and can vary, so don’t be concerned if you 175 is actually 184mm. Sizes are all governed by ETRTO (European Tyre & Rim Technical Organisation). The ETRTO also set and control the design dimensions for wheels as well as tyres.
    60 = Aspect ratio. This is the height of the tyre from the top of the tread to the bead (bead is hidden when fitted to a wheel- see diagram) (I WILL DRAW A PICTURE FOR YOU TO SCAN IF YOU LIKE). The 60 is not a measurement, but a percentage. It is 60% of the width, so that would mean a 175/60 tyre would have a height of 105mm.
    14 = Wheel diameter in inches. Measured from the bead seat of the wheel (not the overall exernal rim diameter).
    Other tyre data: You may have a value such as 91Y written on the side wall. The number represents the maximum tyre load (weight) and can be varied with tyre pressure. The letter is the speed rating. A ‘Z’ rated tyre can be safe over 150mph, a V rated tyre is about 130mph etc...

    6) an other info
    Changing tyre sizes: If you’re vehicle had a 175/60R14, then I would recommend NOT changing that size as it will be matched to the vehicle.
    If you do have to change it, ensure that you remain with the same rolling radius. i.e a 185/55R14 will be similar (to calcuate the rolling radius correctly, you need to use a formula that accounts for tyre deflection; i.e. a 175/60R14 designed tyre diameter = 14inches+(2 x 105mm)=565mm, but it’s rolling radius will be less due to vehicle weight. Therefore a 185/55R14 designed tyre diameter = 14inches+(2 x 92.5mm)=541mm looks smaller, but with a smaller sidewall it will deflect less and therefore have a ‘close enough’ radius when comparing the rolling radius.

    Variation in tyre width as well as profile will affect vehicle performance, and the impact will vary based upon tyre brand and vehicle.
    Most often, people fit larger wheels & tyres with diffent dimensions in all areas (wheel offset, unique tyre size etc.) which completely f*cks up the OE chassis design, but it doesn’t bother them that their car now handles like canal barge with the responsivness of the QE2 because it looks good(!)

    In summary, stick to the approved tyre size AND PRESSURES. Ideally, stick to the approved tyre, but if it’s no longer available, try and go for a good brand name (i.e. Michelin, Conti, Goodyear, Pirelli, Dunlop... in that order!) who will have performed an overcheck with the tyre size they recommend for each vehicel in the aftermarket, so it will be safe.
    If you go for a cheap budget tyre, you will worsen the chassis and loose out when you want to push the vehicle. Additionally, if you go for a tyre which achieves its grip just through the compound (i.e rhymes with Pokyamama...) you will probably notice a distinct difference in adverse weather conditions (plus you will be replacing tyres quite regulary; although I must admit that this particular company have improved recently and are producing more acceptable OE tyres, not just sticky crap used by lotus to get good track reviews from journalists...)

    By James Smith

  • #2
    thanks james and your mate for that info

    i think i will buy some s2 steelies for my s1

    what about yoko tyre's

    Comment


    • #3
      Originally posted by Power House
      thanks james and your mate for that info

      i think i will buy some s2 steelies for my s1

      what about yoko tyre's
      Im trying to get him to do a tyre report on the well known brands, but as you can imagine it will be very broard as theres alot of tyres and each one has specific qualities etc etc,.....really its an impossible task, but im gonna see what we can come up with.

      His main area of expertise is wheel design & Manufacture etc etc, so a report or document on alloys wheel options, wheel quality, construction, performance and manufacturers etc may be a better option.

      Comment


      • #4
        ok cheers

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        • #5
          very interesting read mate

          nice 1

          were gettin loads of info lately bout stuff praise you
          S1, What a ride,,,
          as side-ways as you like it baby
          and some serious speed around those bends

          Comment


          • #6
            yeah I think its a great piece and gives some sound advice - I got so fed up of the same questions being asked - which will happen on a forum - its nice to be able to point people to this.

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            • #7
              Superb info. Thanks.

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              • #8
                Originally posted by artdealer View Post
                Superb info. Thanks.
                no probs, glad to hear any feedback thats good!

                I love this article, mainly because it gives great in depth info about pretty much everything about the rallye steel!!

                Comment


                • #9
                  Like the thread james, quick question on the wheel size 5.5j x 14
                  What would be the recommended size of tyre? 175/60/r14?
                  Could i use 185/60/r14? I know this is not the proper wall height, but i can get them dead cheap and the van only gos a maximum of 70

                  Comment


                  • #10
                    they'd be fine rob, look at what i have on my 5.5x14"'s

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                    • #11
                      does anybody know of any other pugs/cits that used 14 x 6j wheels in the 106 offset (et 15-20)?
                      Its just i can get steel wheels from pug very cheap (£10 for a set of 4) and this would be ideal for my track tyres.

                      Comment


                      • #12
                        Originally posted by boni View Post
                        does anybody know of any other pugs/cits that used 14 x 6j wheels in the 106 offset (et 15-20)?
                        Its just i can get steel wheels from pug very cheap (£10 for a set of 4) and this would be ideal for my track tyres.
                        alot use 14" steels but not sure they would be 6J.

                        You need to ask someone to look on the parts CD for you - post a request thread in the wheel and tyres section.

                        Comment


                        • #13
                          havent been on for a while but glad to see that alot of people have made use of this article (1900+ reads) n

                          Comment


                          • #14
                            dos any1 want to swop sum gti wheels with new tires for sum s2 steels!? please please

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                            • #15
                              Could i put 185/60/14's on s1 steels or should i get s2 steels?

                              Sorry if its a stupid question im new lol

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