80/100 - 21" vs 90/100 - 21" which is better?

Related:
Create New Tag

1/8/2019 6:23 PM
Edited Date/Time: 1/8/2019 6:26 PM

I have been using a starcross 5 soft 80/100-21 front and 110/100-18 rear on my 1980 yz250 and riding tracks with a dry, hard, surface like milestone, perris, and elsinore. I just got a 1981 yz 465 and it has a fairly steep steering angle, so it turns pretty decently, so i was considering going with the larger 90/100-21" starcross front in hopes that it would give slightly better traction on flat, hard, dry surfaces then the 80/100-21", but wanted to know if it will make it noticeably harder to turn or lean or if it will try to climb out of ruts etc with the larger tire. Appreciate any opinions on this from those that have run a 90/100-21" front tire on mx type tracks.

I plan on using the starcross soft or hoosier 25 compound (semi soft) rear in a 120 so i can get the beast to hook up at least a little.

Thanks in advance for any opinions/suggestions.

|

1/8/2019 6:35 PM

This question has come up a few times and I haven’t really seen a solid answer yet. I bought the 80/100 and it’s noticeably thinner than anything else I’ve used

|

1/8/2019 6:40 PM

I run the 90/100 21 front for years now with the kenda washougal tire. Ever since the dunlop 756's went away that's how long. I can't go back to the 80/100 i tired once after running the 90/100 for years. Same tire brand and tread and i went back to the 90/100.

I like the extra grip I couldn't get the feel out of 80/100. I have been running the 90/100 since, even though I'm from the pnw. I've ridden with them on the tracks you mentioned in socal no problems. Even run it on my yz144! And my yz250.

|

1/8/2019 6:49 PM

I’ve gone to a 90 front, 120 rear from a 80 front, 110 rear for the last 7-8 years. Slightly more effort and a little heavier feel to toss from side to side but totally worth it for the better tracking and traction.

|

1/8/2019 6:53 PM

95% of us have no feel for what the bike is doing whatsoever...so it doesn’t even matter.

You might be the 5%....but unless you are a pro rider or professional test rider, probably not.

I always chuckle when “Johnny C class” has a long debate over which brand/size/tread pattern of tires to buy, or if he should run 12 lbs or 13 lbs psi in his front tire, or if that FmF pipe is better than pro circuit...reality is, that dude has no clue what the bike is doing, isn’t riding fast enough for performance flaws in either option to even show up, and couldn’t tell the difference in a blind test. So it doesn’t matter.

|

1/8/2019 6:58 PM

Titan1 wrote:

95% of us have no feel for what the bike is doing whatsoever...so it doesn’t even matter.

You might be the 5%....but unless ...more

"You might be the 5%....but unless you are a pro rider or professional test rider, probably not."

I am in the 5% group, and actually testing and developing off road bikes and atv's was exactly my job at Kawasaki when I worked in their r & d department in the 80's, although I have slowed down considerably since then.

|

1/8/2019 7:03 PM

.... and never turns the throttle all the way to the stop.

|

1/8/2019 7:05 PM

garagedog wrote:

.... and never turns the throttle all the way to the stop.

I do on the start, lol.

|

1/8/2019 7:08 PM
Edited Date/Time: 1/8/2019 7:11 PM

Titan1 wrote:

95% of us have no feel for what the bike is doing whatsoever...so it doesn’t even matter.

You might be the 5%....but unless ...more

barnett468 wrote:

"You might be the 5%....but unless you are a pro rider or professional test rider, probably not."

I am in the 5% group, and ...more

Right on then! Good for you. Then this is a valid discussion for you, though I would say this isn’t the place to have it...very very few with your resume around here.

I’m not in the 5%...even as a vet A class desert guy, I’m an awful test rider. Sand tire on hard pack feels the same to me as a hard tire on hard pack...I just ride the bike. So I won’t be any help for you on this topic.

|

1/8/2019 7:17 PM

I've run all sizes. I found the larger 90/100s really benefited my Yamaha(s) due to their chassis characteristics, but those same size and brand of tires felt terrible on the my KTMs. I never really liked the feel of 80/100s in any bike but find them better on the KTM/Husqvarna then in my Yamaha(s).

I have found a real common ground on 90/90s which seem to offer the best of both worlds. My tire choices have been mostly been between Michelin and GoldenTyre (currently running a GT216AAHB 90/90/21 on the front of my Husky 350 and a Michelin SC5 'soft' 110/100/18 on the rear). A couple of times a year I throw a set of Dunlops on for a comparison but always come back to my Michelin/GoldenTyre combo.

|

1/8/2019 7:35 PM
Edited Date/Time: 1/8/2019 7:40 PM

Titan1 wrote:

95% of us have no feel for what the bike is doing whatsoever...so it doesn’t even matter.

You might be the 5%....but unless ...more

barnett468 wrote:

"You might be the 5%....but unless you are a pro rider or professional test rider, probably not."

I am in the 5% group, and ...more

Titan1 wrote:

Right on then! Good for you. Then this is a valid discussion for you, though I would say this isn’t the place to have ...more

"I’m an awful test rider. Sand tire on hard pack feels the same to me as a hard tire on hard pack...I just ride the bike. So I won’t be any help for you on this topic."

lol, that's ok, you are still probably way faster then I ever will be again. You are also in good company, because Rex Staten wasn't a great test rider either. He could simply make any pos haul ass so it didn't really matter. Eddie Warren wasn't a great test rider either. Team Green actually borrowed me from R & D for the ponca and loretta nationals one year and i was assigned to him and 2 other of their best riders and he couldn't tell much difference in different parts either. Believe me, I would consider trading your skills or theirs in exchange for mine in his area, lol.

.

|

1/8/2019 7:35 PM
Edited Date/Time: 1/8/2019 7:37 PM

Just like on a car, a low profile (80) will have good stability in cornering and less roll, but little cushion effect so it rides rougher. The 90/90 "fatty" is the opposite with great cushion and "floats" over sand and ruts and makes the suspension feel plusher, but moves on you in hard pack and has worse turn in requiring chassis adjustments.

|

1/8/2019 7:47 PM
Edited Date/Time: 1/8/2019 8:01 PM

Monk wrote:

I've run all sizes. I found the larger 90/100s really benefited my Yamaha(s) due to their chassis characteristics, but those ...more

"I found the larger 90/100s really benefited my Yamaha(s) due to their chassis characteristics, but those same size and brand of tires felt terrible on the my KTMs."

I was thinking this might be the case in some instances, but fortunately I am dealing with bikes that are far more similar to each other. At this point I'm leaning towards the larger front, plus, if I get it I can possibly just exchange wheels with my 250 and try both sizes on both bikes. The 250 corners decent now that i finally have it set up the way i want but it pushes/skips, the front tire a little on hard dry turns, but of course that is to be expected, and i haven't tried any other types of tire to compare it to. My other consideration was a hoosier 20 compound front but the hoosier re has not gotten back with me yet to let me know if they make one.

Obviously most any tire works well in a berm, especially if the ground is a bit tacky, but i prefer to take the tight inside of turns whenever possible and there often isn't a berm there.


"currently running a GT216AAHB 90/90/21 on the front of my Husky 350 and a Michelin SC5 'soft' 110/100/18 on the rear)"

I was thinking about another 110/100 for the rear of the 465, but my 250 spins the bejesus out of it if the dirt is a little loose. the engine was built by fmf back in the day, and of course, the 465 makes my 250 seem like an enduro bike by comparison.

|

1/8/2019 8:07 PM

When I tried out the 90's vs.80's years ago I couldn't come to terms with the 90.

The most noticeable difference to me was initiating "turn in" into corners. The 80 went where I pointed it and the 90 would stand the bike up making me have the feeling of falling off to the inside and dabbing my foot. I tossed the 90 and have only used 80's since and every time I ride someone else's bike with a 90 it feels like a pig that won't turn.

|

1/8/2019 8:18 PM
Edited Date/Time: 1/8/2019 8:20 PM

slipdog wrote:

When I tried out the 90's vs.80's years ago I couldn't come to terms with the 90.

The most noticeable difference to me was ...more

Thanks for the info, and my 465 definitely is a pig for a 2 stroke mx bike cuz it weighs around 245 bazillion pounds, however, since it has a much steeper steering angle then my 250 does with the 250 forks in the stock position, i have the option of lowering the tubes on the 465 if it is a little hard to initiate a turn. the tracks aren't fast enough where the extra steering angle will cause a problem on the front. I have ridden 70's model mx bikes with a "desert" tire and absolutely hated the way they turned on more of an mx type track, and that is what i want to avoid if possible, but as with anything, one just has to try it to be certain. it's definitely not cheap to buy one but my plan is, if i get the bigger front tire and don't like it, i can always sell it on ebay for half price, or possibly at one of the races i will be going to as i will be racing calvmx, twmx, and othg as often as possible.



|

1/11/2019 7:33 PM

Johnny Depp wrote:

Just like on a car, a low profile (80) will have good stability in cornering and less roll, but little cushion effect so it ...more

I haven't tried any tires in the last 26 years, so I no longer have anything to compare to, and tire tech has changed a lot since then. I went to elsinore today (there is another odd story there with another well known tire mgf) and the front end stuck extremely well, and i could turn inside any time i wanted, and passed most people by going inside, and i doubt that i got that much better in the last 4 days since i rode there. It was very odd. Anyway, i looked at a 90/90-21 at temecula motorsports yesterday and i would try that size if starcross made one.

Anyway, my plans have temporarily changed because i now have a set of hoosiers coming in the 20 compound, so i will try those first and compare the starcross and hoosier fronts back to back and then decide what my next plan will be. I will try to test them on the elsinore truck track for one, since it is by far the hardest and driest track around.

|

4/4/2021 8:48 AM

Titan1 wrote:

95% of us have no feel for what the bike is doing whatsoever...so it doesn’t even matter.

You might be the 5%....but unless ...more

You don't have to be a pro rider to feel tire roll in corners because of low tire pressure. Maybe take the time to feel what the bike is doing instead of talking trash on the internet.

|

4/5/2021 12:55 PM

80/100 is best in my experience for moto, especially at low speeds on a 'technical' track where there are deeper, longer ruts and multiple lines choices. These are best suited for quicker turn in and tracking.

90/90 is best for a grand prix style track thats faster and rougher. Also works really well off road and in rocky terrain. You can still turn with this size but there is a tendency to want to run out of a rut or just not track well.

90/100 is for high speed high impact and super rough. Such as racing desert, woods, etc. It gives the most cushion and tracks straight and gives great stability because of its footprint. However for quick, fast twitch turning it can be a handful. Most people ive seen dont run this tire at tracks.

Tire size is just one part of the forumla though. Temperature, tire PSI, bike set up, suspension, the bike its self (a suzuki turns better than a yamaha so a crap tire on a suzuki will perform better in turns than a gummy on a yamaha for instance). The most important technical factor I feel is matching the tire with the terrain. Are you in sand/mud? Then dont run an AT-81 and complain at how vague it felt. Pick a MX11.

|