Evening all! I have started work on RPD4 and need some tyre advice, I am keeping the original wheels so I am looking for suitable crossply tyres, the fronts currently have 3.25 X 19 Firestone, the rears 4.75/5.00 X 18 Mudpluggers,
I have found some 3.50 X 19 Longstone Fronts and some Michelin D.R. in 4.75/5.00 X 18 for the rears, are these allowed?
What about Blockley's, they do a 3.50 X 19 and either a 4.50/5.00 X 18 or a 5.50 X 18 in the 3 block pattern
Martin - Goto the ACTC Site. Then Getting Started. Under the Tyre Regulations it lists the tyres that are allowed. If your tyres aren't on the list you can't use them. You can apply to the ACTC tyre officer to add to the list
Both the Blockleys and the Michelin DR's (the latter as a Michelin Confort)are on the list. Don't forget the "two sizes different" rule. So if you go for the 4.50/5.00x18 Blockley (my choice) you must run a minimum of 3.50 on the front. So I would go for the 3.50x19 Chen Shin, which will have better lateral grip which is what a front tyre needs.
Thanks Michael and Simon, I did look at the ACTC list but I wasn't sure if the Blockley's that are allowed were the 3 block type, I agree totally with your recommendation Simon! Now where are the kids piggy banks!!
Blockleys (at least the Longstone copy) are too stiff for trialing unless you have a heavy car, they are no use on my Austin 7, 8 cwt unladen. I use Cheng shin motor cycle tyres. I find a narrow tyre is best for the Austin and I use 3.25 x 18 C117 rear 3.50 x 19 C180 front. My Austin's handling is unstable (extremely twitchy, not safe!) with the Longstone Blockley on the back and Cheng Shin on the front, please be careful!
I think we are homing in on a solution, following an informative chat with Dudley Sterry we think 4.75/5.00 X 18 Michelin D.R on the rear, the same size as the Mudpluggers, and some 4.50 X 19 somethings on the front. The 3 block Blockleys are an option for the fronts. Opinions please!
There are several things to think about; assuming that you want to use RPD4 for serious trialling and that it still has the 1172 Ford side valve engine. You should note that my experience is based on trialling an Austin 7, and more recently a Marlin. But I’m a relative newcomer compared with Dudley Sterry!
Front tyres It would be interesting to compare the weight of a 3.25x19 as found on the car with a 4.50x19. I run 165x14 on the Marlin on the front and 185x14 on the back, the 165 are significantly lighter. I was once told a pound saved at the front is worth two on the back!
Rear tyres Two considerations; gearing and grip.
Gearing I find that with a lot of rough sections it is difficult to go slowly enough without either slipping the clutch or bogging the engine down. Equally, the car needs to have enough go to be able to spin the back wheels vigorously. So as I run a low ratio first gear in my Austin 7 I find I need to use the 3.25x18 to get a low enough gear to give me enough power to do what I need to do. The Marlin has more than enough power; the problem comes in going slowly enough. For example on a hill like Bamford Clough I will partially slip the clutch most of the way up to avoid excess speed and engine bogging down. The 3.25x18 measure very roughly 80 inches in circumference while the 3.50x19 measure 83.75 inches, so the smaller tyre is about 4.5% smaller which makes a noticeable difference.
Grip With the hills we have nowadays in VSCC trials I find that the narrower tyres grip just fine. I haven’t tried the Marlin on the 165s at the back and would like to do so. You can conclude from this that on most of the sections that we have these days I’m not convinced that wide tyres are better. But I would be really interested in someone else’s opinion on this
Martin - Goto the ACTC Site. Then Getting Started. Under the Tyre Regulations it lists the tyres that are allowed. If your tyres aren't on the list you can't use them. You can apply to the ACTC tyre officer to add to the list
ReplyDeleteMichael
Both the Blockleys and the Michelin DR's (the latter as a Michelin Confort)are on the list.
ReplyDeleteDon't forget the "two sizes different" rule. So if you go for the 4.50/5.00x18 Blockley (my choice) you must run a minimum of 3.50 on the front. So I would go for the 3.50x19 Chen Shin, which will have better lateral grip which is what a front tyre needs.
Thanks Michael and Simon, I did look at the ACTC list but I wasn't sure if the Blockley's that are allowed were the 3 block type, I agree totally with your recommendation Simon! Now where are the kids piggy banks!!
ReplyDeleteBlockleys (at least the Longstone copy) are too stiff for trialing unless you have a heavy car, they are no use on my Austin 7, 8 cwt unladen. I use Cheng shin motor cycle tyres. I find a narrow tyre is best for the Austin and I use 3.25 x 18 C117 rear 3.50 x 19 C180 front.
ReplyDeleteMy Austin's handling is unstable (extremely twitchy, not safe!) with the Longstone Blockley on the back and Cheng Shin on the front, please be careful!
I think we are homing in on a solution, following an informative chat with Dudley Sterry we think 4.75/5.00 X 18 Michelin D.R on the rear, the same size as the Mudpluggers, and some 4.50 X 19 somethings on the front. The 3 block Blockleys are an option for the fronts. Opinions please!
ReplyDeleteThere are several things to think about; assuming that you want to use RPD4 for serious trialling and that it still has the 1172 Ford side valve engine. You should note that my experience is based on trialling an Austin 7, and more recently a Marlin. But I’m a relative newcomer compared with Dudley Sterry!
ReplyDeleteFront tyres
It would be interesting to compare the weight of a 3.25x19 as found on the car with a 4.50x19. I run 165x14 on the Marlin on the front and 185x14 on the back, the 165 are significantly lighter. I was once told a pound saved at the front is worth two on the back!
Rear tyres
Two considerations; gearing and grip.
Gearing
I find that with a lot of rough sections it is difficult to go slowly enough without either slipping the clutch or bogging the engine down. Equally, the car needs to have enough go to be able to spin the back wheels vigorously.
So as I run a low ratio first gear in my Austin 7 I find I need to use the 3.25x18 to get a low enough gear to give me enough power to do what I need to do.
The Marlin has more than enough power; the problem comes in going slowly enough. For example on a hill like Bamford Clough I will partially slip the clutch most of the way up to avoid excess speed and engine bogging down.
The 3.25x18 measure very roughly 80 inches in circumference while the 3.50x19 measure 83.75 inches, so the smaller tyre is about 4.5% smaller which makes a noticeable difference.
Grip
With the hills we have nowadays in VSCC trials I find that the narrower tyres grip just fine.
I haven’t tried the Marlin on the 165s at the back and would like to do so.
You can conclude from this that on most of the sections that we have these days I’m not convinced that wide tyres are better. But I would be really interested in someone else’s opinion on this
stick a 1700 rip rorin x-flow in it and don't worry about the tyres !
ReplyDeletecarl shorly toyota power would be the way to go makes a crossflow seem tame
ReplyDelete4.00x19 Avon SM? Longstone Tyres £71.00
ReplyDeleteSuch a hooligan that Carl, I blame his father! :)
ReplyDelete