Ray13/60 Posted September 15, 2018 Report Share Posted September 15, 2018 Hey, recently bought these wheels and will have to fit longer studs before trying to fit. Not sure if I have made a mistake buying them really. Will a 15 inch wheel actually fit in those arches - looks close !! would be good to hear of anyone who has had a positive result before trying or if you think its a stupid idea, even trying. please say - thanks, ray Link to comment Share on other sites More sharing options...
Anglefire Posted September 15, 2018 Report Share Posted September 15, 2018 Personally I am not keen on them. Only because it looks wrong on an older car. But I’m not the one that has to live with them? as long as the rolling radius is the same they should fit - unless they are too wide that is. Different radius and you’ll have to alter the speedo drive gear. 1 Link to comment Share on other sites More sharing options...
Clive Posted September 16, 2018 Report Share Posted September 16, 2018 I have had them on a spitfires, but they are more generous with the wheel arches. I also had 15" maestro wheels (essentially the same) on a herald based kitcar years ago, but the rears fouled the tie-rods and I needed spacers. That may have been because of the tyre width or a different offset? Tyre size will be important, 185/55 is what I had on the spitfires. If you get longer studs you will want the m12 type (freelander, there are plenty of threads about them) but choose the ones where the thread goes almost all the way so you can still use them with steel wheels. The reason you need m12 is that there are no safe-to-use std sized (3/8) wheelnuts, they are all too small and only just touch the edges of the holes though the wheels. You can bodge it using "grayston escort wheel washers" but that route is not as good as the m12, and much more expensive. Hopefully somebody will be along to give you a definitive answer..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 16, 2018 Report Share Posted September 16, 2018 One thing you must consider with increased wheel and tyre rolling diameter is you reduction the brake efficiency Pete Link to comment Share on other sites More sharing options...
Nick Jones Posted September 16, 2018 Report Share Posted September 16, 2018 A few people have fitted MGF wheels to Heralds and Vitesses. Tyre choice is also relevant to arch fit and rolling radius. There is a gentleman who hillclimbs a Mk1 Vitesse and he some times uses MGF wheels fitted with wide sticky tyres. I know he has some wheel arch mods but not sure whether these were actually needed for this wheel/tyre combo or what the tyre size is. Don't think he comes here that often but is a regular poster on the Sideways Technologies forum under his "Oldtuckunder" handle. Doesn't seem to cause any braking problems on that car. Clive is right about the wheel studs. Standard studs are too small and too short. Nick Link to comment Share on other sites More sharing options...
Ray13/60 Posted September 16, 2018 Author Report Share Posted September 16, 2018 Thanks everyone, really helpful Clive great to know that studs can also be used with steel wheels. Didn't want to do the work and then have to change the studs again, if the wheels didn't work out Nick, I'll check out oldtuckunder. Great forum, cheers ray Link to comment Share on other sites More sharing options...
Paul H Posted September 16, 2018 Report Share Posted September 16, 2018 This link might help Paul Link to comment Share on other sites More sharing options...
SpitFire6 Posted October 27, 2018 Report Share Posted October 27, 2018 On 16/09/2018 at 09:50, Pete Lewis said: One thing you must consider with increased wheel and tyre rolling diameter is you reduction the brake efficiency Pete Hi Pete? A reduction because of what? Cheers, Iain. 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 27, 2018 Report Share Posted October 27, 2018 lets just say the bigger rolling diameter has more leverage over the same sized brake the tarmac makes more torque at the centre , same applies with acceleration the bigger the overall diameter you need more torque for the same acceleration or a lower axle ratio or a slower car, you takes your pick Pete Link to comment Share on other sites More sharing options...
JohnD Posted October 27, 2018 Report Share Posted October 27, 2018 I've no doubt that Alan "oldtuckunder" has modified his suspension, at the very least making it a lot stiffer, so less movement. A small chassis Triumph notoriously - and largely unjustifiably - loses adhesion at the extreme, because of gross camber change as the suspension moves, especially at the back. Modern suspensions are much better at keeping the tyres vertical to the road. Modern radials have a much flatter tread than old crossplies, and flexible walls, so that the tread stays flat on the road, but there's a limit to what they can do. Worse, you would need a much lower profile of tyre to fit inside the wheelarch. Once that limit is reached, the tread tilts on the road, and adhesion and traction are lost. If you want to use wider wheels, stiffen the suspension, and take other action to limit camber change, else those big fat wheels wont be useful. John Link to comment Share on other sites More sharing options...
SpitFire6 Posted October 27, 2018 Report Share Posted October 27, 2018 1 hour ago, Pete Lewis said: lets just say the bigger rolling diameter has more leverage over the same sized brake the tarmac makes more torque at the centre , same applies with acceleration the bigger the overall diameter you need more torque for the same acceleration or a lower axle ratio or a slower car, you takes your pick Pete Hi again Pete, I understand about torque implications, but rather small on a road car (+/- 5%)? I was referring to the "Brake efficiency". You referring to tyre/road or maybe pad/disk? Cheers, Iain. 1 Link to comment Share on other sites More sharing options...
johny Posted October 27, 2018 Report Share Posted October 27, 2018 looking on the tyre comparison sites you could get 175 60 15 of which theres quite a range and they would be almost exactly the same size as my 165 80 13 (slightly bigger diameter than original) so as long as the wheel offset is the same there should be no clearance problem.... 1 Link to comment Share on other sites More sharing options...
Colin Lindsay Posted October 27, 2018 Report Share Posted October 27, 2018 Provided you no longer need to use the suspension, cos there's absolutely no going-up-and-down room left... Seriously: check the lip on the inside of the wings as it can eat into the sidewalls of tyres if the wheels are too wide; it happened on my GT6. Link to comment Share on other sites More sharing options...
NonMember Posted October 27, 2018 Report Share Posted October 27, 2018 2 hours ago, Spitfire6 said: I understand about torque implications, but rather small on a road car (+/- 5%)? I was referring to the "Brake efficiency". You referring to tyre/road or maybe pad/disk? It's the same thing. The brakes don't act on the road - they act on the hub, which then applies a slowing torque, converted into a force by the tyre. So in exactly the same way that larger tyre diameter reduces your acceleration, it also reduces your braking deceleration. Link to comment Share on other sites More sharing options...
SpitFire6 Posted October 27, 2018 Report Share Posted October 27, 2018 7 minutes ago, NonMember said: It's the same thing. The brakes don't act on the road - they act on the hub, which then applies a slowing torque, converted into a force by the tyre. So in exactly the same way that larger tyre diameter reduces your acceleration, it also reduces your braking deceleration. Hi, so you are saying if wider than standard there is no difference in stopping distance? Cheers, Iain. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 27, 2018 Report Share Posted October 27, 2018 Well as I see it unless you change the weight or the pressures the footprint area regardless of tyre size wont change Pete 1 Link to comment Share on other sites More sharing options...
johny Posted October 27, 2018 Report Share Posted October 27, 2018 No Iain its not width theyre talking about but overall tyre diameter. If you held your drive shaft in your hands and tried to stop it rotating while someone else turned the wheel (obviously with it free) you would find it harder the bigger the overall tyre diameter even though your assistant applies the same force in each case because they will have more leverage. Its the same for your brakes as the pads will have to clamp harder for a given rate of deceleration the bigger the overall tyre diameter. However the most sensible thing is to stick as close as possible to the original overall diameter so you can avoid this and other possible issues.... Link to comment Share on other sites More sharing options...
Adrian Cooper Posted October 27, 2018 Report Share Posted October 27, 2018 57 minutes ago, Spitfire6 said: so you are saying if wider than standard there is no difference in stopping distance? As I understand it, friction is proportional to the force of the road surface acting on the tyres and this is stated as Pressure X Area This is equal to the weight which is distributed to each tyre, assuming a smooth, uniform and level surface. Therefore the friction is the same regardless of the width of the tyre; for a wide tyre the area is large but the force is small and for a small tyre the area is small but the force is large. In the real world, the road surface is not smooth and a wider tyre has more chance of making contact with more high spots on any given patch of tarmac, but the advantage may be minimal. Adrian Link to comment Share on other sites More sharing options...
Herald948 Posted October 27, 2018 Report Share Posted October 27, 2018 1 hour ago, Pete Lewis said: Well as I see it unless you change the weight or the pressures the footprint area regardless of tyre size wont change Pete I would agree; "contact patch" might be the key here, and that area can vary significantly amongst various brands of tires in any given size, be it stock size or whatever. And as others have suggested, there's the rather significant range of camber in the rear suspension in particular, so.... Link to comment Share on other sites More sharing options...
Colin Lindsay Posted October 28, 2018 Report Share Posted October 28, 2018 12 hours ago, johny said: No Iain its not width theyre talking about but overall tyre diameter. If you held your drive shaft in your hands and tried to stop it rotating while someone else turned the wheel (obviously with it free) you would find it harder the bigger the overall tyre diameter even though your assistant applies the same force in each case because they will have more leverage. Think of it the other way - if you close a valve by turning a small stopcock, it requires force; if you close the same valve by turning a huge wheel, it requires less effort. The valve still closes the same way but the bigger diameter wheel gives the same force for less effort at the rim - greater leverage. If you're braking, a smaller wheel will require less force / friction than a bigger one. Link to comment Share on other sites More sharing options...
rlubikey Posted October 28, 2018 Report Share Posted October 28, 2018 I've always thought that tyres work, not only by friction (and yes, I was paying attention during my physics lessons!) but also by keying into the road surface, which I think is a different mechanism. This means that, for the same road surface, a softer tyre will have more grip, and a wider tyre (larger footprint) will also have more grip. Presumably there has to be enough weight to force the rubber to squirm into the crevices in the road, so presumably there's a footprint to weight & compound softness limit. If anyone has any insight on this, I'm eager to learn. Cheers, Richard Link to comment Share on other sites More sharing options...
Colin Lindsay Posted October 28, 2018 Report Share Posted October 28, 2018 Presumably, the squishier the tyre, the more it will conform to the contours of the road, so I presume that if you have an uneven road surface, then soft rubber will fill the minute gaps and crevices which will no doubt give better grip. It also probably mean that tyres like this will wear amazingly quickly. A hard rubber tyre will last longer but is more inclined to slide by bridging the gaps and cracks, and not conforming to them therefore having less grip. This is too complicated for this time of the morning. Link to comment Share on other sites More sharing options...
poppyman Posted October 28, 2018 Report Share Posted October 28, 2018 Personally i think it does not matter how wide or how big in diameter a wheel is, you only require the same brake pressure. You are after all only trying to stop the same weight. Yes i understand the the driveshaft to wheel theory, but that is going into the pulley and leveridge theory. Also stopping all depends on the amount of rubber on the ground and the surface. Tony. 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 28, 2018 Report Share Posted October 28, 2018 Pressure is load x area you can mix and match the simple equation differeing tyre compounds and structures will have some effect on the efficiency to grip absorb and roll but the foot print area is dendant on the above , not just on its own but has an awful lot to do with it We had a glass plate you could draw the foot print under various conditions Pete Link to comment Share on other sites More sharing options...
Nick Jones Posted October 28, 2018 Report Share Posted October 28, 2018 It's not the wheel diameter that matters but the rolling radius of the wheel/tyre combination. Dependent on tyre choice the actual difference between wheel sizes could be negligible. Even if the 15" wheel combo had a slightly larger rolling radius, the effect on braking effort will be negligible. As regards tyre contact patch, when comparing narrow tyre and wide tyre, for a given tyre pressure and vehicle weight, the area of the contact will be the same, but different shapes. The narrow tyre will have a narrower but longer contact and the wide tyre a wider, but shorter contact. This assumes that the tyre is meeting the ground squarely. If this is not the case (rather likely with Herald suspension, especially at the rear), then the wide tyre may do less well, especially if it is lower profile, as it's sidewalls would need to flex more to keep the wider contact patch on the road. Bottom line - a narrow, taller profile tyre is likely to give more consistent grip with a suspension that gives a wide range of camber angles. That said, it's possible to get decent results from a 15" wheel tyre combo (even TRR hillclimb champion class-winning results) albeit on a car with modified suspension including a camber compensator at the rear. Nick Link to comment Share on other sites More sharing options...
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