Tire considerations

[OliverB]

If you are referring to the front tire, the standard replacement size is 90/90x18. I have 100/90x18 on the front and it does clear everything nicely. Rear is 120/90 and no clearance problems. My son has a Dunlop 404 130/90 on the rear of his '81 and it clears everything.

 

[Ebola Monkey]

I'm not at home, but I think mine has a 100/90 on the front. It just fitsin thefender, but I relaced a 2.15 rim to the stock hub. Back is definitely 120/90, and doesn't rub, on stock spoked rear.

 

[jayel]

Hey Drewpy I just realized this but my rims are frt 1.85 x 18 AND RR 2.15 x 18 but my manual says they should both be 3.00 x 18 WTF? Is it just wrong.

1.85 and 2.15 are the rim sizes (width), 3.00x18 is the tire size

 

[sharps09]

Thanks, the Kenda K761 im getting require tubes, but I'll hold off on the strip.

 

[drewpy]

If you have the cast wheels, no need for strips or tubes. Those rims were made for tubeless tires.

If you are referring to the front tire, the standard replacement size is 90/90x18. I have 100/90x18 on the front and it does clear everything nicely. Rear is 120/90 and no clearance problems. My son has a Dunlop 404 130/90 on the rear of his '81 and it clears everything.

SOHC mags definatly need tubes, you are running a risk of deflation otherwise!

 

[OliverB]

Interesting. No tubes in the tires I took off and none installed with my new tires. Mag rims are marked "For tubeless tires". Why is there a risk of deflation with tubeless tire rims? The rims are made by JWL. They have made rims for just about everything worldwide for decades.

 

[drewpy]

Interesting. No tubes in the tires I took off and none installed with my new tires. Mag rims are marked "For tubeless tires". Why is there a risk of deflation with tubeless tire rims? The rims are made by JWL. They have made rims for just about everything worldwide for decades.

you have aftermarket rims then?

the original yamaha rims for sohc yams are for tubed. its to do with the rim profile keeping the tyre from deflating

 

[OliverB]

Drewpy,
I don't doubt your knowledge of these bikes and I am newly back into cycles after many years away but I am confused about this tire/tube/tubeless issue. As a former moderator of a large international motor scooter forum, I know the importance of posting accurate information so as not to mislead others and maintain the safety of their vehicles.

I was away from home today for an Easter family visit so i could not double check what I was fairly certain about concerning the marking on my rims. No, I don't believe my rims are aftermarket but are original to the cycle and identical to others pictured on like cycles. All markings on the rims are cast in markings except for the marking referring to use of tubeless tires. That mark is stamped in, as though it was added, and reads "SUITABLE FOR TUBELESS TIRES". Is it possible the rating and/or rim design was different for the U.S. market or changed for 1980? I surely don't know as this is the only '80 or '81 I have seen with mags. My son's '81 has wire wheels.

While I said there were no tubes in the tires I had removed last week, I wasn't present when the tires were switched out. No mention was made to me by the shop owner of tubes present or the need for new tubes. I will check with him tomorrow.

This whole thing is very curious and I don't want to spread incorrect information. According to a Yamaha service manual I downloaded for the XS360-400, the XS400G/SG,H models came equipped with tubeless rims. The tubeless designation is not listed for previous years. That would seem to cover 1980 and 1981 XS400 models with cast rims. I can only go by what I see on my own cycle and what I found in the Yamaha manual.

 

[hmusket]

There was quite a discussion and some controversy about this issue recently on the XS650 forum (I also have a 1979 XS650 that I started working on a couple years ago, but ran into some issues, another story for another day). From what I could see from my own research at the Star (yamaha) website, http://www.starmotorcycles.com/star/parts/home.aspx
Yamaha put tubes in the mag wheels through 1979. In 1980 they went tubeless. So for safety I would stick with tubes for those years.

In another life I owned a Fiat 850 spyder, with steel rims. I replaced tires, tubeless were put on. Everything seemed ok until I took on a highway trip, tires began deflating as Drewpy said, and I could smell the rubber. When I went to the tire shop a call to Fiat verified that those rims needed tubes.

 

[bcware]

Interesting.The rims are made by JWL. They have made rims for just about everything worldwide for decades.

JWL is a standard, not a manufacturer. If you're interested: http://en.wikipedia.org/wiki/JWL_standard

 

[drewpy]

yamaha were one of the first manufacturers to have cast wheels so made them heavy and had to have tubes AFAIK they went tubeless for the DOHC bikes (certainly in Europe) as the technology caught up. 1981 was when the DOHC was released so yours would have benefitted with the new tech?.

Checking my manual 3F9, 4R4 and 14V models used tubeless tyres and the rest were tubed.

peeps need to be aware of this as not all cast wheels are tubeless

 

[OliverB]

Ok, sounds like we have shed some light on this issue. Looks like Yamaha equipped their XS400s with tubeless tire rims starting in 1980 - at least for the U.S. market. On my bike, I have put on more than 1K miles in the past year and have not experienced deflation issues. Since the Yamaha service manual specifies tubeless rims for '80 & '81 here on the XS400 and since my rims are stamped "Suitable for ...", I will continue with my wheel/tire setup as it is. Others will have to check and make that decision when tires are changed out on their bikes. Since our bikes are quite old and may have gone through mods by previous owners, anything is possible in terms of the vintage of the wheel on the bike when purchased in more recent times.

BTW, the same Yamaha service manual lists 120/90x16 as the stock size rear tire for '80 and '81 bikes. Front size is still listed as 3:00x18 in that service manual - interesting that the new size is listed for the rear but not the front.

My bike was manufactured in Feb., 1980. I do not have the original owner's manual but I do have one on the way for my exact year and model bike. It will be interesting to see if this issue is addressed in that manual.

I recently purchased a rear 18" disc brake wheel to use if I decide to change out my rear drum brake wheel. Later today I will check that wheel.

BC,
Thanks for the heads-up on the meaning of "JWL", didn't know that!!

hmusket, thanks for the additional info and link.

 

[bcware]

There could have been a change in the alloy rim manufacturing process when the transition from tubed to tubeless took place, but I think it is more likely that tire technology, and not the wheels, was holding everyone back.

If the xs400 was capable of higher speeds I might be more concerned, but I am guessing it wont even do a ton; this probably isn't enough to really stress a modern tubeless tire. Even the cheap Kenda tires I bought have an H speed rating (130mph). I find it hard to imagine that, being so light and slow (relatively speaking), an xs400 could possibly stretch or open up the sidewalls under any circumstances. A tube is not going to stop a tire from coming off either.

If anyone has any anxiety about this, one can always add a tube to a tubeless tire. Some research on my part leads me to believe the general consensus is that when running a tube in a tubeless tire one should drop the effective speed rating by one grade; so, H (130mph) would drop to U (124mph). Thus xs400s with modern tires (save for that guy with the turbo-charged one) should not be affected by this very much.

 

[OliverB]

Yeah, I have seen top speed rating listed as 90+ mph for our bikes. You are correct about modern tires. The "H" rated tires do have an awesome stiff bead and sidewall. Both front and rear are listed as tubeless tires for SG and H models ('80 & '81) but the front is still listed in the old size designation of 3:00 while the rear is listed in the new size designation of 120/90 in my Yamaha service manual.

 

[briansal]

Old thread but I was just doing some research/reading. I seem to have a 1.60 wire wheel up front. According to drewpys chart the widest tire I can go is 3.00 which is stock I believe. I was hoping a 3.50 Duro HF308 would fit. Bcware you have the same year bike did you go up in rim width to accommodate the wider tire? Also does anyone have any feedback on the duro tires. Thanks.

 

[bcware]

I use kenda challengers (not knobby).

I am running 100/90/18 in the front and 110/90/18 in the rear with stock rims.

The front is maxed out with the original fender.

I removed the chain guard from the rear.

The rear can accept 110/90/18 or 120/90/18, but the larger size is a bit of a gamble in my opinion and will depend on the particular profile/shape of the tire you choose. If it were me I would not buy a 120/90/18 for the rear unless I had verification of that specific model tire from someone else on here.

If you're searching for more info remember that later years have wider swing-arms and 16" rear wheels.

If you search in inch sizes your options will be very limited and probably expensive I am going to guess. Anyone still marketing inch sizes is probably just taking advantage of people who don't know how to do the conversion.

Honestly, I have only extremely rarely heard anything negative and substantiated about ANY tire manufacturer. Most people who give negative reviews are just making shit up. They don't even own the tire. People leave negative reviews about products they don't like all the time online even when they don't own the product. Try finding negative reviews in a forum from verified buyers with documentation including photos or videos. I wouldn't listen otherwise. Most sites don't require reviewers to be verified buyers. Some, like bikebandit, do indicate if the reviewer is a verified buyer. Even if you don't buy from bikebandit.com it is a useful place to look at reviews because they do a lot of sales and the reviews are marked as verified or not.

 

[briansal]

Thanks Bcware i am not running any front fender so width isnt an issue there. But Drewpys chart scared me. But i see wide tires on these bikes all the time i didnt think they went with wider rims. the duros come in 3.00 3.50 4.00 and the 4.00 is $60 shipped which is very decent in Canada. I wanted to go 4.00's front and back but i think 3.50f and 4.00r would be a good compromise to keep the handling a little better.

 

[Specdog]

Thanks Bcware i am not running any front fender so width isnt an issue there. But Drewpys chart scared me. But i see wide tires on these bikes all the time i didnt think they went with wider rims. the duros come in 3.00 3.50 4.00 and the 4.00 is $60 shipped which is very decent in Canada. I wanted to go 4.00's front and back but i think 3.50f and 4.00r would be a good compromise to keep the handling a little better.

But Drewpys chart scared me.

Good, it should because it was created by engineers who know about these things.

I wanted to go 4.00's front and back but i think 3.50f and 4.00r would be a good compromise to keep the handling a little better.

You've read the chart, you know the recommended tire for your 1.60 rim is 2.50 or a 2.75 is acceptable and the largest tire considered safe is 3.00. I think you know that is your answer to "what is the largest tire available?"
Now I know lots and lots of people squeeze on tires that are too big for the rim. They either don't know it is wrong or don't care. Some ignore engineers advice and go for looks over function. I'm no engineer but let me try and explain what happens when you force a too large tire on a rim. The sidewall becomes rounded and stiff when mounted in the too small rim and therefore looses some/most of its flexibility. The bead sits in the slot designed into the rim but the extra side forces try and move the bead off the rim. This is exacerbated at higher speeds and when driving over rough roads or pot holes. Your tires need lots of flexibility in the sidewall to perform properly. BYW the sidewall is what puts heat into your tire. You want about 12% rise in temp, not more and certainly not less. Another popular misconception is larger tires give you a greater contact patch. Not if you don't have the proper rim. When you deform the sidewall putting it on a rim not designed for the tire, the contact patch actually decreases. Think about how your tire sits with a designed sidewall profile, now push in the sidewall at the bead and you can see how the tire deforms and the contact patch rounds further lessening the contact patch.
The more larger tire and the farther you stray from engineers recommendations, the greater the chance becomes of your tire actually popping off the rim. A conscientious tire installer won't mount that tire for you.
I reread this before posting and didn't like how I came off as being preachy. I don't know how to change this, I'm just trying to help.

 

[xschris]

If you are looking for the best performance then 90/90-18 in the front and 110/90-18 in the back Bigger tires add mass and more circumference using more of the bikes limited power. Also what specdog said on safety

 

[briansal]

No it's not preachy specdog. Safety should be number 1. I was just wondering how all these modified bikes are running wider tires than stock. Including Bcware who is running a 3.50 tire and as far as I can tell rides hard and long trips. I found another chart that says a 3.60 tire will fit a 1.60 rim but a 90/90 18 should not. Each brand is going to be a little different as well. I'm not sure if tubes play any role in how tires react being a little wider than recommended. Or using a 6ply with stiffer sidewalls. But I agree with the don't know don't care attitude especially on heavily modified bikes.