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Tire size
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rbucklin
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PostPosted: Mon Aug 06, 2018 8:35 am    Post subject: Tire size Reply with quote

Hi All,

New to the forum. Grew up with a dune buggy in the family, it disappeared sometime about 20 years ago. Pop just got tired of seeing it in the yard and sold it without consulting any of his 8 kids. It was a Manx clone tub with a different nose that we always thought was cooler than the manx nose piece. I always thought if I ever saw that style again I would have to buy it. Well....

So now I find myself in the middle of a dune buggy rebuild. It's been off the road for a few years so now in the process of sorting needs and todays question is tire size. I was going to either change out the trans for a freeway flyer or have a lower final drive installed in the current trans, but the guys at Bow Wow suggested putting a taller rear tire (about 2in) and lowering freeway rpms that way. I was planning on a taller/wider rear anyway so now trying to figure out appropriate sizes.

I'm going with powder coated stock steelies, 15x5.5.

Anyone have any knowledge or experience with this?

Thanks in advance!

Russ
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vwracerdave
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PostPosted: Mon Aug 06, 2018 9:02 am    Post subject: Re: Tire size Reply with quote

Welcome to The Samba.


You need to include engine size/power, tire size, and transaxle gearing all together to end up with an enjoyable ride. What size engine are you planning on building? What transaxle gears do you currently have? What size rear tires do you want to get the profile look of your Dunebuggy?

How will you be using your Dunebuggy? Spirited city driving or long distance trips?

When you run taller than stock gearing the lower RPM's causes the engine cooling fan to turn slower and the engine runs hotter or possibly develops overheating issues.
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JaredJ
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PostPosted: Tue Aug 07, 2018 3:35 pm    Post subject: Re: Tire size Reply with quote

Bruce Meyers recommends no more than a 28 inch diameter tire with a stock 1600 engine (or even a 1776) with a stock transmission. a 255r70-15 tire is 29 inches in diameter just for example. A 255r60-15 is 27 inches. The transmission is the weak link.....a 4:37 ratio is a safe bet.
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clonebug
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PostPosted: Tue Aug 07, 2018 7:38 pm    Post subject: Re: Tire size Reply with quote

I run 275/60-15 tires which are 28 inches tall.... it gives me a 70 mph cruise at 3100 rpm with a 4.12:1 67 transmission..
I think it is perfect with a buggy.
I hav run is this combo with a 1500 sp, a 1600 dp and also with my 1679 turbo.
The first two would run short of power after 80 mph but anything below was fine.
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rbucklin
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PostPosted: Thu Aug 09, 2018 8:48 pm    Post subject: Re: Tire size Reply with quote

I have a very low mile 1640(ish) DP, a 67-69 4 lug swing axle stock trans. Best guess is 4.12 r&p. The motor came out of another tube frame buggy I acquired and it is very healthy.

The car will be for semi spirited street use (cops here Seattle suburbs are ticket happy, and this will draw attention).

In the Seattle area it is impossible to get around without getting on the freeway a few times a day so would like to run somewhat lower rpms. Not super hot here so cooling should be ok.
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EVfun
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PostPosted: Fri Aug 10, 2018 1:01 pm    Post subject: Re: Tire size Reply with quote

I would recommend you start by sticking what you have on the car, front and back and measuring. How wide works? How tall fits? What balance front to rear is pleasing to your eye? Buggy bodies vary a lot in the fender size and shape.

From there you look at what is a reasonable rear tire height. I recommend a bit more rpm, I like to see between 2700 and 3000 rpm at 60 mph -- stock to just slightly taller. Checking my own 2 buggy builds, it seems I've set up for 61mph at 3000 rpm both times. There are not many chances to go over 60 mph in the Seattle area, even on the freeway.
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slalombuggy
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PostPosted: Fri Aug 10, 2018 1:27 pm    Post subject: Re: Tire size Reply with quote

Since you are sticking t0 a fairly skinny rim I would suggest a 215/65/15. They are 26 inches tall and a decent width. Since they are only an inch taller than stock they won't affect the gearing that much.

I run that size and really like it.
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EVfun
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PostPosted: Fri Aug 10, 2018 5:15 pm    Post subject: Re: Tire size Reply with quote

A couple thoughts came to mind.
1. Stock Bug wheels where never 5.5 inches wide. The stock style wheel you have are a common aftermarket item. The offset may have varied over time or between manufacturers. I recommend measuring your wheels.
2. Buggies generally have wider rear wheels. Using one size all around should be possible, but tire selection will need careful consideration. Perhaps 145R15 front and 215/70R15 rear. The idea being to use about the smallest recommended and tallest recommended tire, balanced to your buggy body fenders.
3. Make sure the wheels you install are what you WANT. It is such a big part of the look and more normal options are that that different in price. Search used too, here and craigslist, and other sources around you. If tacky chrome plated 5 spoke baja style wheels are part of the era look you want contact me. I have old wheels I removed to install stock and widened 14 inch Bus wheels.
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didget69
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PostPosted: Sat Aug 11, 2018 12:35 pm    Post subject: Re: Tire size Reply with quote

EVfun wrote:
A couple thoughts came to mind.
1. Stock Bug wheels where never 5.5 inches wide.


Sports Bug & Special Edition wheels (Lemmerz) were stock from Factory & were 5-1/2" wide.

Bryan
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rbucklin
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PostPosted: Tue Aug 14, 2018 6:51 am    Post subject: Re: Tire size Reply with quote

OK, so decisions made and money committed. Took the U.S. 8 spoke wheels that came with the car (15x6, 15x10) in for blasting and powder coating in a nice sort of metallic pewter gray. Tire sizes are 205/60r15 front and 235/70r15 rear. Tire height will be about stock 25.7 in front and 28 in back. rear will be a little heavy but not bad.
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vwracerdave
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PostPosted: Tue Aug 14, 2018 9:06 am    Post subject: Re: Tire size Reply with quote

I would suggest you get smaller rear tires 27" or less. With a 1641 and stock transaxle gearing you are not gonna like the 28" tire. No matter how cool it sounds to turn lower RPM's you must keep the engine in the power band the VW engineeres designed the engine for. When you turn less RPM's the fan turns slower and does not cool the engine as well and causes the engine to run hotter.



There won't be any spirited city driving with 28" tires.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
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Watch my racing video's http://www.youtube.com/user/okvwracer/videos
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rbucklin
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PostPosted: Tue Aug 14, 2018 3:56 pm    Post subject: Re: Tire size Reply with quote

I understand the point. My brother is running 275/75r15 in an original manx with a 1776 dp with no temp problems. I ran the size and wheel weight by my guy at bow wow and he thinks it should be fine. I do have an oil temp gauge and will monitor closely when it's up and running. Thank you for the caution.
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