Tire Size

[deek]

Hello All

Is a 120/90-18 Michelin substitute a 400x18 on the rear of a 72 6 Day???

Dale

 

[Bob]

Too big. Here's a jpeg conversion chart. Save it to your hard drive for future reference.

http://members.cox.net/dynobob/photos/tire_conversion_chart.jpeg

[rd400pi]

Bob,
  Thanks for the conversion chart. BTW, I didn't see the edit stuff either and, I logged on per earlier suggestion.  What am I missing?
  (This is cool, I just found the edit which is via the icon with the pencil.  I was thinking about edit options PRIOR to posting but, this edit function appears to be AFTER you have posted.  Learning is good.)
  Mike Husted (rd400pi)
  72/74 Six Day & 76 MC5 250



Edited by - rd400pi on 04/19/2003  12:47:39 PM

[deek]

Thanks a million Bob, for the chart. Mike, I
don't have the the pencil and trash can, : (
.

Dale

 

[Dwight Rudder]

Actually the 1972 125cc Six Day came with a 350 X 18 Metzler, not a 400 X 18.  Try and stay with a vintage looking tire. Modern tires look strange on a vintage bike. I wish they would outlaw modern looking tire on Vintage race bikes. Go with a 350X18 Cheng Shin or a 4.10X18 Cheng Shin , Kenda, or Duro
I put a nice set of Continental TKC80 tyres on my Zündapp GS125 in a 90/90X21 ( same as a 300X21 ), and a 350X18 rear. Not cheap but work great and look similar to late 60's and Early 70's Metzler's.
If using Other brands,
Cheng Shin - Use C755 model ( Metzler copies ) tires in the 410X18 ( same as 3.75 )and 350X18 Rears. If you have a Jackpiner or HareScrambler use the 4.60X18 ( same as 400/425X18 or 450X18 Motocross Metzler )
OR you can use the C183 model ( Barum Copies )
in the 350 and 400 X18 sizes.
Pirelli - MT16 model tires , Modern tires that look vintage. I use them on my modern bikes also. Great front tire 300 or 80/100X21
400 or 110/100X18, good for strong 175cc to 360 cc bikes.
Kenda - Use the K257D Metzler copies.
300X21 and the 410X18 ( 3.75 ) for the small bikes
Duro - Use the HF335 / HF905 Cross Country tires. Metzler look alikes.
80/100X21
410X18 = small tire 350 size
460X18 = small tire 400 size

another hint is use the Moose Racing Foam tubes.  Not a full Bib Mousse insert.
These have a foam insert with a small inner tube to make installation easier and so you can adjust airpressure and prevent flats. Much cheaper than Michelin Bib Mousse.
Still looks vintage.
Cher'o,


Dwight Rudder
7 time ISDT / E medalist
7 time National Enduro Class Champion.

[Larry Perkins]

Those Cheng Shen tires look like Metzlers but they hold for crap in MX.  If you want to look the part it works, if you want to go fast it doesn't.  There is a big difference in what is acceptable in the woods and what is acceptable on the track also.  

For me looking the part is not important only having every chance to win and be safe.  That is why I wear a modern full coverage helmet, body shell, knee brace, and boots.  I also use modern tires that hold better than they did back in "The Day".  I also have modern cables, modern tank stickers, modern shocks, and modern re-made fenders because they all work better than back then.  I generally don't have museum bikes but ones that are vintage legal racers useing every legal modern advantage.  I guess it all depends on where priorities are.  Mine are usually focused more on winning than preserving an era.  To each his own.  It matters not why we came here merely that we are here.

 

[Lew Mayer]

Larry,
 From your point of view for performance,what tires do you like. Looks aside. While you're at it, the sizing also for a jackpiner.

Lewis A Mayer

[Dwight Rudder]

I thought the whole point of Vintage bikes was preservation of an Era. If you want to win at all costs go to modern races. I do.
You can do both. If you race a Jackpiner or larger the Pirelli MT16 tires are top notch. I use them racing my "Modern bikes". They work great. The look good also on vintage bikes. You can get too much traction. Vintage bikes are easier to ride with the right amount of tire slippage. Helps in cornering and keeping the bike on the Pipe.
I agree that the Cheng Shin tires are not my first choice but they aren't as bad as you say either. Not on vintage bikes. I prefer the other brands I listed.  A bit stiffer rubber compound that isn't quite as squirelly.  I don't believe we should be trying to make modern bikes out of Vintage machines.  Kind of defeats the purpose of restoring the old machines isn't it ?  After all it IS about preservation of an Era.
IMHO,

Dwight Rudder
7 time ISDT / E medalist
7 time National Enduro Class Champion.

[deek]

quote:
Hello All

Is a 120/90-18 Michelin substitute a 400x18 on the rear of a 72 6 Day???

Thanks for all the info, greatly appreciated!!



Dale

Dale

 

 

[Dwight Rudder]

No, Not really.  Although a small tire for the size it is more suitable for 200cc bikes and mid sized 4 strokes.  I found to be too much traction for even a 340cc XR Honda. OK for a 400cc XR.
Cher'o

Dwight Rudder
7 time ISDT / E medalist
7 time National Enduro Class Champion.

[maicobuddy]

I'll have to agree with Mr. ISDT (not an insult) I use the Pirelli MT-16's on both my 74' Montesa VR250 & 78' Montesa VB250 they look the part & work very well on almost any terrain...and are not very expensive fronts can usally be bought for less than $60.00 and rears for around $70.00...maicobuddy

 

[Larry Perkins]

Okay,

Here is the argument again of preservation or competition.  First off let me say Dwight, I love you so this is not personal.  By stating the whole purpose of vintage is the preservation of an era is not accurate.  Everyone does this for different reasons and to varying degrees.  I love the heritage of these and other Vintage bikes.  I love the time period that I first raced them in because it was a less stressfull time.  But when the rubber band pops or the gate drops I could give a rats rear that the model I am racing came with Girling shocks, aluminum fenders, steel rims, and 32mm forks.  I also don't care if in "The Day" I would have had a Bell Super Magnum on with a Joffa and Full Bore or HIPOPINT boots.  

That all looks good in the museum or at a display but when the Vintage race begins for me that same bike will have Works Performance alloy bodied shocks(because Girlings sucked for MX and back then I wouldn't use them then and Works work), plastic fenders(because they are more pliable and practical for racing than $100 aluminum fenders), alloy rims(because they are lighter and that is rotational weight that is ever so important at the start and accelerating out of corners), and 35mm forks(because they flex less and have better damping than the 32mm).  And I will be wearing a modern full coverage composite helmet(because I have never had a cavity and like my teeth and because the closeset you will see to me putting a Joffa on is putting one on ebay), Alpine Stars Tech 8 boots and carbon fiber knee brace(because Tech 8's are the safest boot out and because my knee isn't).  I will also be sporting a bodyshell(because "The Day" gave me the  gift of a couple of broken collarbones because there were no bodyshells).

Now when it comes to racing my main objective is to win.  The many guys that travel the AHRMA circuit in hopes of a title spend alot of dollars in the chase.  I think there are many of them that want every conceiveable legal advantage to increase the odds of there success.  That holds true for me whether it is 1973, 2003, or 2003 racing a 1973.  

I am wise enough to know though that the next guy is perhaps out there for another reason.  I respect that reason just as I expect respect in return for my reasons to Vintage.  

As always it is important that it happens and not so important how it came to happen.


Did someone say something about tires?
100-175=3.50X18 or equivalent
250=400X18 or equivalent
400=4.50X18 or equivalent

I think the smaller ones(100-175) need to rev to keep good speed and the smaller tire helps.  Realize that most of my experience is MX related.  I think the 4.50 on the 400 keeps it from revving which is the way to ride it for the common man.


 

[rob w]

Well said Larry, my thoughts exactly. I also know where Dwight is coming from, and can totally respect him for his beliefs. I like that about you Dwight.

The thing with these Pentons is, you can't even find the parts to restore one correctly, and if you're lucky (or wealthy)enough to do so, the furthest thing from your mind should be to go out and compete with it.

I've worked hard to make my race Penton look like a Penton did back in "the day" . Now after one ISDTRR and two MX races it's sadly transforming back to the "whipped out" look. When the time comes to start replacing worn out parts again, I'm going to use what ever works, not what looks the most correct for that era. Take shouldered Akront rims for example, they really look the best on a 74-75 Penton, but I won't be lacing those up next time around. Thanks, I like these debates.

 

[Dwight Rudder]

Some shocks and rims can't be replaced. Thus alloy rims and Works Performance shocks or Ohlins are used. I will have to say that these shocks I mentioned are head and shoulders above Girlings and Koni. But I strive to make it look of the period or a period modification. Tires are one thing you can do to make the bike look right. There are decent tires that look of the period. Some comprimises do have to be made but in moderation.
IMHO,
Dwight

Dwight Rudder
7 time ISDT / E medalist
7 time National Enduro Class Champion.