Blackwaters vs. Mudrunners vs. Vampires
#12
08-31-1999, 12:44 AM
Polaris recommends for the front tire height to remain the same because the speedo on 99 and newer models is located in one of the front wheels. If you get a larger tire the speedo will not display an accurate speed. You will read a slower speed with the larger tires. Other than that, there should be no significant disadvantages to a larger tire up front.
#13
08-31-1999, 08:07 AM
I’m glad to see this subject of height and sizes come up. There’s a far bigger issue (than speedo accuracy) being missed here. In AWD with the front hubs engaged all four tires are “locked” together by the drive train. If the tire sizes (or heights) differ too much it will put great stress on the mechanical components. Think about it; let’s say 26” rears travel 8’ in one revolution and 25” fronts cover only 7’ (arbitrary example). Since the components they’re both connected to are turning at the same rate of speed (revs) something’s going to get stressed and give. It’s either going to be the drive train or one set of tires will be scuffed from either being pushed or dragged.
We’re talkin’ theory here. AWD used properly would only be engaged on terrain that would allow slippage, reducing mechanical stress. But still, it would be possible to be on asphalt or hardpack with the AWD on and spin the rears just enough to engage the front hubs. If this would happen there’d be a whole lot’a stress goin’ on.
My stock 25” SP500 tires mounted on the bike and inflated to the recommended pressure measure ¾” different in height, with the rears being taller. Since it came this way from Polaris I can only assume the machine is geared or otherwise set up to accommodate this difference. When I put aftermarket tires on it seems logical to attempt to maintain a height difference close to this same ratio. My 25” Kenda Bear Claws only missed the mark by 1/8” (7/8” difference, front to rear). That was a very comfortable margin.
After reading here that Polaris recommends 26” rears and 25” fronts for Mud Runners I assumed it was to maintain something close to the stock tire front / rear ratio. Then a friend bought 26” Mud Runners all the way around (against my warning about Polaris’ recommendation) and called me to say his fronts are 1 1/8” shorter than the rears. That’s already 3/8” more than the stock difference, not tooo bad, but imagine how much shorter the 25” fronts would be! Later it occurred to me that I didn’t ask if he’d checked the tire pressure and since they were just mounted it may have been off, skewing his measurements a bit, but not by a lot.
Today I’m picking up a set of 26x12x10 and 26x9x12 Mud Runners at a Goodyear dealer. From my friend’s experience it just doesn’t make sense to me to put 25s on the front. Once they’re mounted and properly inflated I’ll post the height difference.
------------------
FloodRunner, on the Wisconsin River
[This message has been edited by floodrunner (edited 08-31-1999).]
We’re talkin’ theory here. AWD used properly would only be engaged on terrain that would allow slippage, reducing mechanical stress. But still, it would be possible to be on asphalt or hardpack with the AWD on and spin the rears just enough to engage the front hubs. If this would happen there’d be a whole lot’a stress goin’ on.
My stock 25” SP500 tires mounted on the bike and inflated to the recommended pressure measure ¾” different in height, with the rears being taller. Since it came this way from Polaris I can only assume the machine is geared or otherwise set up to accommodate this difference. When I put aftermarket tires on it seems logical to attempt to maintain a height difference close to this same ratio. My 25” Kenda Bear Claws only missed the mark by 1/8” (7/8” difference, front to rear). That was a very comfortable margin.
After reading here that Polaris recommends 26” rears and 25” fronts for Mud Runners I assumed it was to maintain something close to the stock tire front / rear ratio. Then a friend bought 26” Mud Runners all the way around (against my warning about Polaris’ recommendation) and called me to say his fronts are 1 1/8” shorter than the rears. That’s already 3/8” more than the stock difference, not tooo bad, but imagine how much shorter the 25” fronts would be! Later it occurred to me that I didn’t ask if he’d checked the tire pressure and since they were just mounted it may have been off, skewing his measurements a bit, but not by a lot.
Today I’m picking up a set of 26x12x10 and 26x9x12 Mud Runners at a Goodyear dealer. From my friend’s experience it just doesn’t make sense to me to put 25s on the front. Once they’re mounted and properly inflated I’ll post the height difference.
------------------
FloodRunner, on the Wisconsin River
[This message has been edited by floodrunner (edited 08-31-1999).]
#14
08-31-1999, 02:16 PM
#16
09-01-1999, 08:50 AM
OK all, my new 26” Mud Runners are on my SP500 and here’s how they stack up. On the machine, at 5 psi each, the 26x12x10 rears stand 26 5/8” tall. The 26x9x12 fronts stand 25” tall. This leaves us with a difference of 1 5/8” front to rear with the fronts being shorter. The difference between the stock tires was ¾” with the fronts also being shorter. Now, the only thing I have different than stock on this tire setup is I am running ITP steel wheels in front (stock rears). The ITPs are one inch wider than stock (stocks are 6”, ITPs are 7”). A wider wheel will give you a shorter tire because it allows the tire to spread sideways more. A narrower wheel will force the tire to be taller, to a point. My friend who put the same tires all around his SP500 on stock wheels was only showing a 1 1/8” difference between front and rear. I don’t know what his tire pressure was but I have to assume the ½” difference between his results and mine were due to his narrower stock front wheels giving him a ½” taller tire.
Given the height difference I DEFFINATELY would not recommend the 26” rear and 25” front combination. I’d stay with all 25” or all 26”. In fact, I’d guess that a 25” rear and a 26” front (the opposite of Polaris’ supposed recommendation) would yield results closer to the stock size differences, but I’m not going to go there. I chose the 26” tires for better performance in mud and added ground clearance.
I paid $350 + tax for the set including mounting (removing my Bear Claws and mounting the MRs). It took some haggling to get that low. One Goodyear dealer told me his cost was $337 + shipping so if you’re shopping stick with high volume dealers or mail order.
The couple miles I put on these tires yesterday was on gravel or sand. My first impressions were, they are a heavy tire and I expect them to hold up well in rocky terrain. From the feel of the rubber composition I’m guessing tread wear will be good, but that’s a guess. The sidewalls are stiff, stiff enough that I wouldn’t be surprised if they’d run-flat in a pinch, although I’d guess you’d have to do something pretty drastic to flatten one. The front tread has the appearance of being more aggressive than the rear, probably because the lugs are equally as tall on both but the fronts are closer together and on a narrower tire. I noticed lighter steering right away, and plan to try the fronts at the recommended maximum air pressure of 6.5 psi to see if there’s even more improvement. That should give me a little more tire height in the front too but we’ll see how much the ride suffers. On sand they did better than my stockers or the Vamps and about the same as my Bear Claws, but I really don’t ride sand.
The rest of my evaluation will start in a week and a half when we go up north riding for the weekend. I'm going to find the nastiest mud holes around (already know where to look) and give’em hell!
------------------
FloodRunner, on the Wisconsin River
[This message has been edited by floodrunner (edited 09-01-1999).]
Given the height difference I DEFFINATELY would not recommend the 26” rear and 25” front combination. I’d stay with all 25” or all 26”. In fact, I’d guess that a 25” rear and a 26” front (the opposite of Polaris’ supposed recommendation) would yield results closer to the stock size differences, but I’m not going to go there. I chose the 26” tires for better performance in mud and added ground clearance.
I paid $350 + tax for the set including mounting (removing my Bear Claws and mounting the MRs). It took some haggling to get that low. One Goodyear dealer told me his cost was $337 + shipping so if you’re shopping stick with high volume dealers or mail order.
The couple miles I put on these tires yesterday was on gravel or sand. My first impressions were, they are a heavy tire and I expect them to hold up well in rocky terrain. From the feel of the rubber composition I’m guessing tread wear will be good, but that’s a guess. The sidewalls are stiff, stiff enough that I wouldn’t be surprised if they’d run-flat in a pinch, although I’d guess you’d have to do something pretty drastic to flatten one. The front tread has the appearance of being more aggressive than the rear, probably because the lugs are equally as tall on both but the fronts are closer together and on a narrower tire. I noticed lighter steering right away, and plan to try the fronts at the recommended maximum air pressure of 6.5 psi to see if there’s even more improvement. That should give me a little more tire height in the front too but we’ll see how much the ride suffers. On sand they did better than my stockers or the Vamps and about the same as my Bear Claws, but I really don’t ride sand.
The rest of my evaluation will start in a week and a half when we go up north riding for the weekend. I'm going to find the nastiest mud holes around (already know where to look) and give’em hell!
------------------
FloodRunner, on the Wisconsin River
[This message has been edited by floodrunner (edited 09-01-1999).]
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