1. Sjacob

    Sjacob Puttering Along

    So, the tires on my P50 (or Piffy, as I have recently decided naming it) are more than 15 years old, and oddly enough they are not all of the same dimensions...
    The front tires and the spare are all 145-80-R13, while the rear tires are 155-80-R13. This, combined with the age and the fact that some of them are leaking, has led me to the conclusion that I should probably get some new tires for my trabi, and then the question arises; what tire size should I buy?

    The standard for trabants is as far as I know 145-80-R13, but I have also seen somewhere that one may use anything between 135 and 165.
    I am toying with the idea of buying 155-80-R13, but I would usually prefer using the original dimensions and honestly I am considering the bigger dimensions mainly because they are much easier to get!

    Any objections? Will 155 tires screw up the speedometer reading or steering, as the added width also adds to the diameter of the wheel? And what about the aesthetics, any objections to the look of the 155 tires? Here is a profile picture of my trabi with the bigger rear tires:
    [​IMG]
    (By the way, this picture is from before I had done anything to the Trabi, so at this point it didn't run, was in the process of breaking in two at the middle, and had no brakes on the rear tires...)
  2. Keri

    Keri Leader

    My other car uses 155/80R13 tires. After trying one on, it seemed awfully close to hitting the inside of the wheelwell.
    So we special ordered the 145/80R13 tires which have been great.

    Sometimes I see "wrong size" tires on the cars I work on at my job. A lot of times, this causes the tire to rub against things, usually on turns and/or bumps.
    People often do this for a softer ride or because the bigger tires are cheaper.

    One size bigger won't make very much speedometer error. It will make it under-read the speed and distance slightly.
    With the correct sized tires, my speedometer is almost perfectly accurate and the odometer is only off by .1-.2km over 8km

    By the way, most Trabi wheels are designed for tires with inner tubes. These are the rims with 4 "slots".
    Tubeless tires will work with or without tubes on Trabi rims BUT.....
    If you are not using inner tubes, the tire can easily unseat and blow out, especially upon hard cornering and with low pressure.

    The newest, mid 80's style Trabi rims with 8 slots do appear to be tubeless compatible, as they have ridges to keep the bead seated.

    I should probably repeat this in the Tech Help section...
    Tim S likes this.
  3. Sjacob

    Sjacob Puttering Along

    Keri, you joining this forum is the best thing since sliced bread :)
    Good input, I will try to get the 145/80 for my little Piffy, but in case that is not possible I have decided to try 155/70 instead, or other variations in the same direction.
    Piffy's rims are from various parts of the 80's and seem to handle the tubeless tires that are on them adequately, so I think that should be OK.
    (In case anyone does not know, the production year for the rims are stamped on them)
  4. vdubbin

    vdubbin Loyal Comrade

    I know this is an old thread, so forgive the bumpage, but for anyone else looking for tyres sizing etc, there's a handy online tool at http://www.miata.net/garage/tirecalc.html that calculates the difference that resizing the tyre/wheel combo makes to speedos etc. miatatirecalc.png
    Justin and Keri like this.
  5. Keri

    Keri Leader

    That's a nice calculator thing for figuring out tire diameter.

    We also need to consider tire width, as our wheels and wheel openings are very narrow.

    A lot of times people put a too-wide tire on a narrow rim which can damage the tire.
    A wider tire, even if a matching rim is used, can hit things particularly on turns or bumps.

    On my 100km of daily commuting I see a lot of cars with giant jumbo low-profile wheels stuck by the side of the road with busted suspensions....
  6. 60chevyjim

    60chevyjim Puttering Along

    lots of times the cars with the big rims use such a low profile tire that when they hit a pothole it pinches the tire and cuts it and sometimes cracks the rim too causing a flat tire .most of the time ruining the tire and the rim. its so funny you will see a car with 3 24 inch rims a 1 boyoing tire on it just to limp around. I see it a lot here in north carolina.
    it seems like they try to see who can stuff the most inches of rim on a car , just so they can say I have bigger rims than you..
  7. turbofiat124

    turbofiat124 Loyal Comrade

    Keri, you mean my 81 Trabbi rims should have inner tubes in them?

    I don't know about the P50 models but my Trabbi came with 13" SR 145 tires with mismatches brands. Two were made in Poland, one from Slovakia and one from Czechoslovakia. After I had the tires demounted and rims sandblasted, I was shocked at the condition they were in. Maybe when the guy demounted them this caused the the sidewalls to split. I can't believe I put 2500 miles on these things!

    This is in the United States but the only supplier that sells the correct size tire is Coker. But they are not too bad at $75 a piece. These are made by Vredestein.

    The other alternative is to use 13" 175 80 series which tire stores claim is the same size but it's not. I have a set of these on my Yugo.

    Most tire stores that offer this size sell no name brand Chineese 1 ply tires.

    My Yugo came with 13" SR 145 tires. So I had to go with the above version. These are mounted on Fiat X 1/9 alloys which are about an inch wider and have a different offset than the Yugo steelies and I had to remove the metal in the wheelarches to get rid of scrubbing issues. They work but don't really fit.
  8. Keri

    Keri Leader

    Using tubeless tires on rims intended for tubed tires is a very old issue, dating back to the introduction of tubeless tires around 50 years ago.

    Basically, an old school rim was made to make dismounting the tire very easy. As one pushes the sidewall inward, unseating it, no resistance is made. This makes dismounting the tire without damaging the tube easy. If the tire unseats while driving aggressively, no air is lost from the tube and the tire re-seats instantly as soon as the sideward force is removed.

    Tires meant for use with tubeless tires have a retention hump or bead. This is a raised ridge about an inch from the edge of the rim. This makes it very difficult to unseat the tire from the rim, so we need to use specialized tire machines that exert great force to unseat tires mounted on these rims.
    This makes roadside dismounting of the tire for patching or replacement practically impossible.

    If a tubeless tire is used on an old type rim, it is possible to unseat the tire while driving at which point all of the air blows out suddenly.

    Many people have driven with tubeless tires on old rims with no problems, but the potential exists, especially if the tire is low on air.

    So if you arr running a tire without a tube on an old type rim, make sure to maintain the air pressure.
  9. turbofiat124

    turbofiat124 Loyal Comrade

    Keri, funny you should mention loosing air pressure on tires. I have trouble keeping air in the tires on my Yugo. But it's the fronts only, particuarly the driver's side that lost the most air pressure.

    This is the Yugo I replaced the original 1100cc engine with a Fiat 1500cc and added a Saab turbo. The car has so much torque steer, scoots sideways and will spin the tire in 2nd gear on dry pavement at full throttle. Apparantly 1800 lb front wheel drive cars that came with 55 hp engines were not meant to be hopped up to 110 hp.

    Awhile back I moved the rear tires to the front and vice versa because I thought I had a wheel bearing going bad and wanted to rule out the tires. I typically don't rotate the tires on this car. Why bother if it goes through a set of fronts every 3K miles?

    Now I am noticing the tires that had been on the rear for years are now loosing air pressure. I thought it was a poor seal on the tire. Or the wheel itself. These are tubeless rims but are Fiat alloys.

    So perhaps the tire pushing and pulling sideways under full throttle is what's causing the tires on the fronts to loose pressure?
  10. Keri

    Keri Leader

    Tubeless tire air loss usually comes from:
    Puncture
    Poor sealing at bead, that is where the tire contacts the rim,
    Leaking valve stem
    Porous or damaged tire
    Porous or cracked rim.

    By the way, some air loss is inevitable with tubeless tires. Even a non-moving spare tire will lose all of its air over a few years. For a moving tire, especially a low-profile tire with relatively low internal volume of air, it's reasonable to expect 1-2 psi a month air loss.

    In your case, where you're using tires and wheels never meant for the car, it's possible to spin the tire on the rim. It's also possible the tire could be the wrong width for the rim, which can lead to poor sealing or tire damage.

    What we see a lot of in Chicago is alloy wheels corroding at the bead area. The rough surface causes air leaks. Also, the hole for the valve stem corrodes, allowing air to leak out there's too.

    One thing to keep in mind when servicing tubeless tires:
    As the car is driven, the tire flexes and moves slightly in relation to the wheel. So, the bead sealing area needs to be smooth or else air leaks out as things squirm around. Using the wrong width tire for the wheel will amplify this effect.
    Very often someone will try to seal the bead with a kind of glue/paint substance called bead sealer. This works great for a spare tire which doesn't move, but seldom repairs a leak for long on a moving tire.
  11. Keri

    Keri Leader

    OK, here's my crude illustrations depicting the tire-to-rim interface.

    The first drawing represents a tubeless tire on a modern rim, with a retention ridge (A) on the rim. 8-slot Trabi rims are like this.
    This ridge or hump, helps prevent the tire from unseating while driving.
    It also makes tire service difficult, as the tire must be forced over this hump with great force to remove the tire.
    Like most tires, there is a steel cable (B) built into the tire that keeps the diameter of the mounting/sealing area stable.
    On tubeless tires, the air pressure inside the tire pushes the tire bead, (C) against the side edge of the rim with great force, causing an effective seal.
    As the tire sidewall flexes quite a bit, there is some movement at this contact area, which often becomes polished.
    If dirt or corrosion build up on the sealing area (C), it forms an uneven surface and air leaks out.

    The middle drawing is of a traditional tube tire on its traditional style rim. Trabi rims with 4 slots are like this.
    The tire contacts the rim at the same "bead" area, but does not depend upon this contact to seal the air in.
    The air is kept sealed within the Inner Tube.
    This type of wheel usually has no retention ridges. As a result, servicing the tire is much easier.
    During hard cornering, the bead might unseat momentarily but no air is lost from the inner tube which will force the bead back in place as soon as the lateral force is reduced.

    The third drawing is what you get when you put a tubeless tire on a traditional rim.
    The only thing keeping the tire bead pressed against the rim is air pressure. This contact is also what seals the tire to the rim and keeps the air in.
    If the tire is subjected to enough lateral (sideways) force, it will overcome the air pressure, the bead will unseat and the air will suddenly "blow out".
    If the tire is inflated properly, particularly at pressures of at least 2 bar / 30psi this is extremely difficult to accomplish, so many people are convinced that driving with tubeless tires on traditional rims is perfectly safe.

    And it is sort of safe.... mostly. Just don't corner extremely hard especially if you don't check your tire pressure frequently.

    tire to rim1.jpeg tire to rim2.jpeg tire to rim3.jpeg



    So, If you're going to race that Trabi, better use tubes in those tires or get the 8-slot rims!

    Good luck!
    Justin and Matteo like this.
  12. turbofiat124

    turbofiat124 Loyal Comrade

    HAH! I've had issues with magnesium and alloys where I've dunked the wheel in a bathtube to find the leak and see air bubbles coming out from around the bead. My solution was unscrew the stem the diflate the tire and appy either sticky brake caliper grease or a dried dishwashing liquid.

    In the case of the mags I have on my Fiat 131 which were loosing all their pressure in a couple of days I applied the dishwashing liquid and it worked.

    I tried the brake caliper grease on my Fiat alloys I have on my Yugo and has worked to some extent.

    When I complained about the air lose to the tire store he said I'd have to put tubes in them which I didn't agree with.

    One time I purchased brand new American Racing wheels for an 86 Prelude and one tire kept going flat. Eventually after bringing the car back 5 times he finally fixed it. I don't know if he put a tube in it or what he did but after the 5th time he finally fixed it.
  13. 60chevyjim

    60chevyjim Puttering Along

    when I assemble my tires and rims I allways spray whitewall tire cleaner on the rim and tire where they seal before putting any air in it.
    it seals the tire very well . I fixed some leaking chrome plated aluminum Cadillac rims . that the chrome was peeling from where the tire seals by removing the peeling chrome and then lightly grinding the rim to clean it and then painting it with several coats of spraycan primer sealer..
    they never leaked again ..:)
  14. trabant601

    trabant601 Loyal Comrade

    I can't tell from the thread which tire you actually used. Which one was it. The 80 and the 70 in those tire sizes is the profile height of the tire from rim to tread (someone please correct me if I am wrong). 80 is called for on a Trabant. I did buy and mount some 145-R70-13 but have not used them yet, that car is not road worthy at this time. I can clearly see that the tires are shorter but I like the width (145). When I imported my first Trabant (bought it Dec. 1989, cleared customs Feb. 1990) I found 145 R80/13 for very cheap all over the place. Those are all gone now in the states (still easy to find in Germany) I now use 155 R80/13 and there is no side effects on any of my cars. Sears has 155 R80/13 that you can buy and carry out to mount yourself.
  15. 60chevyjim

    60chevyjim Puttering Along

    Sjacob I think that your car looks great with the big and little tire combo on it.
    I would keep it that way with all new tires, big and little..
    also it is one of the coolest trabant kombis I have seen on here. I love the color too..
    I love the look of the wagons ,but your earlie version is the best looking of the 2 different style wagons.
    I want one of each wagons , a round body and the later square one like the one in my toy hotrod kombi pix.
    in real life my toy one would have a chevy 327 V8 with 4spd. used for drag racing and car shows..
  16. trabant601

    trabant601 Loyal Comrade

    I recently sold my 327. I still have the 250. No plans to put it in a Trabi, I will keep it in the Bel Air. 1968
    What was the different sizes on front and back? Martin in the UK (Bristol) put a different suspension on his Trabant and used 135 R 80/13 to reduce road friction. His Trabant has been converted to electric. He stopped by here in Hobart one day while he just happened to be in Indiana.
  17. trabant601

    trabant601 Loyal Comrade

    Wartburg353W and Justin like this.
  18. trabant601

    trabant601 Loyal Comrade

    I expect these to arrive any day now. The price and shipping for 4 tires at under $200 is like what I would expect to pay for this size in Germany where there are many many levels of tire. I will let you know when they arrive. See the link above to see them listed.
  19. Wartburg353W

    Wartburg353W Loyal Comrade

    This is a great site. Thanks for sharing. I have bookmarked it. I will need tires next summer for one car and I'm not really happy with the look of the ones I bought last year for the other car. Wartburg takes 165/80/13. I put on 175/70s and they look too small.
    Justin likes this.
  20. trabant601

    trabant601 Loyal Comrade

    I know, I got some 145 70 13 for some nice sandblasted (by a nephew) and primed and painted and clear coated by me wheels. NH mounted and balanced them for me. They are very short but there were NO 145 80 13 to be had at that time. Now I might want to swap them. I sent a message with my order that there is demand for this size and if they dont believe me, to contact me with the deals to share with the demand.

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