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Old 10-20-2011, 01:49 AM   #1
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Default T1N tire size

What's the tallest tire I can put on my 06 sprinter? I'd like to get the speedo a little more accurate and bring the RPM down.
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Old 10-20-2011, 02:37 AM   #2
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Default Re: T1N tire size

I put Toyo MT 245/75/16's on mine and now the speedo is right on and the OD is now slow
BUT I have a 3" lift and had to hammer the lower back edge of the front wheel well a bit.
Your results may very!

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Old 10-20-2011, 12:15 PM   #3
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Default Re: T1N tire size

We just put a set of 245/75/16 copper AT3's on our '06. They are about as big as I would want to go and still have some snow clearance.
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Old 12-10-2011, 01:46 AM   #4
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Default Re: T1N tire size

http://www.tacomaworld.com/forum/tirecalc.php try this it is a good site
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Old 12-10-2011, 03:47 AM   #5
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Default Re: T1N tire size

Cruising the forum, it's been said that anything larger in diameter than 235/75 or 215/85 will hit the mud flaps. 215/85 is also said to correct the speedo. There's not much room in the wheel wells, so I wouldn't go for max size tire if you are in muddy or slushy areas.
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Old 12-13-2011, 07:20 PM   #6
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Default Re: T1N tire size

I found myself stuck in florida sugar sand and decided to upsize my tires. I have the 15 inch rims on my 2006 Sprinter so instead of buying new rims to move up to 16 inches I followed the 245 75R15C size and found a much less sinking feeling.

I have to note that the edge of the tire does matter for the front tires. I had a set of Nexxin tires in the larger tire size and they are fine though at 50 PSI they are at the lowest pressure I would consider usable. I would have preferred to buy a larger set of the commercial GoodYear tires I had been using but the local goodyear shops will only install manufacturer's original size and after a bad day having to dig out my Sprinter 2500 van with a pair of bottle jacks, a wheeled jack on a wooden board and a strap-puller hooked to a tree when I sank up to my axel in sugar sand in my own back yard I wanted more displacement.

I make the note about the edges after one of the special ordered Nexxin tires was punctured irrepairably right before a long planned long drive trip. To get on the road the firestone dealer here that sells nexxin tires had a more expensive Bridgestone tire in stock that they let me have for the same cost. So I went with that model just to get on the road. The new tire had a slightly less rounded shoulder and I left it on the front tire not noticing anything until later. After my wife said what is that sound I found that the new tire would make contact during low speed tight cornering in parking lots. I was able to straighten that out by moving the odd tire to the rear and haven't had a problem since but you should watch clearance when getting new ones installed as the edges vary by model even on the same size tire.

The bigger tires give me slightly less mileage (maybe one less MPG), make the vehicle slightly more challenging when empty in high cross winds (it's the same when loaded), and make the seat slightly higher to get to when mounting (half an inch or so), but I no longer dread getting stuck when I pull my travel trailer onto the dirt road to a campground.

The change in handling is not significant except for the afforesaid lack of sinking but I think in the next version I will hunt for the higher pressure tires I really wanted (taking 80 PSI rears down to 50 is a big deal but the fronts were already 50 PSI on the factory doorplate so it wasn't that big of a change). Overall I would not reccommend the 50 PSI nexxin tires due to the flex I feel from them. I feel I needed to get 10 ply instead of 8 ply to make them ride right. We'll see when next I reboot.
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Old 12-14-2011, 11:24 PM   #7
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Default Re: T1N tire size

I'm a bit confused by this thread, until rading this I would have assumed that the manufacturer spec tyres are the correct size for the speedo?

Waiting to be educated.
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Old 12-14-2011, 11:55 PM   #8
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Default Re: T1N tire size

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Originally Posted by Philj View Post
...
are the correct size for the speedo?

Waiting to be educated.
I can give you my take on it. For the NAFTA Sprinters with stock size tires it seems that the speedo runs a pretty consistent 3 mph over as compared to a GPS mph indication. My 2004 holds to that. Interestingly with stock sized tires the odometer seems to be spot on.

One theory is that Merc didn't want anyone complaining that they got a speeding ticket because the speedometer was reading low. Another is that for safety reasons they want you to think you are going faster than you really are.

Whatever the reason behind it, it seems to be by design being that the odometer is correct and the speedo is off when stock sized tires are mounted. Maybe Sprinters in the rest of the world don't have these differences built in?

YMMV. (Wow, one of the few times this acronym actually applies.) vic
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Old 12-15-2011, 12:31 AM   #9
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Default Re: T1N tire size

I find it interesting that the odometer is not matching the speedo. What you are saying is if for one hour you held a constant 50mph indicated on the speedo a gps would show 47mph. Over the same hour your odometer would have gone up 47 miles not 50? When I eventually get some time I may have to drive between some mile markers with a gps and find out what mine does!

I thought the Australian and UK design rules allowed for 10% innacuracy so your speedo could under or over read by 10% (and in reality most were pretty close to being accurate to within tyre wear and pressure ranges) I know a few people who will sit at the speed limit plus nearly 10% in the belief that their speedo is accurate and the police cant issue a fine until you are more that 10% over the speed limit (A belief I'm not willing to test)

Having checked my assumption with the Australian Design Rules it seems that pre 2006 plus or minus 10% was allowed. After 2006 the rule changed so that speedos cannot under read at all and can over read by a maximum of 4kmph + 10%. Eg: if you were travelling at 100kmph in a post 2006 vehicle your speedo could legally read 100kmph to 114 kmph.

Im guessing there is a similar sort of NAFTA rule.

Incidently whist trying to find out the ADRs I found a page that claimed the folowing: "When vehicle manufacturers install a speedo at the factory, the speedo has been calibrated using data that assumes the vehicle is fitted with new standard tyres inflated to full pressure, on standard rims, and usually the tyre circumference has been measured before the wheel is put on a vehicle or when the vehicle is on a hoist (no load on tyre). When they test the car for compliance with the ADR, the speedo will invariably produce an over-read result."

It seems my mileage will vary indeed
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Old 12-15-2011, 02:18 AM   #10
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Default Re: T1N tire size

Quote:
Originally Posted by bchappell View Post
The bigger tires give me slightly less mileage (maybe one less MPG), make the vehicle slightly more challenging when empty in high cross winds (it's the same when loaded), and make the seat slightly higher to get to when mounting (half an inch or so), but I no longer dread getting stuck when I pull my travel trailer onto the dirt road to a campground.
Just curious, but did you calculate your new MPG with a correction in a larger-diameter tire that should come in at approximately 4% larger than a stock 235? So if you were getting 24mpg with the OEM size, and are now getting 23mpg without taking into account variation in tire size, that would equate to 23.92mpg.
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