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110 or 120 rear tire on a R75/5?
- Thread starter j_withers
- Start date
42906
Themason
I run the narrowest tire that won't slide under power. Wider rear tires make the bike respond slower and require more effort at the bars to turn in. That might be an acceptable trade for a race bike putting over 200 horses to the ground wile the rider's knee skims the ground, you need the big contact patch to control that power and the rider is an athlete, but on public roads, say playing in second gear on some tight little squiggle in the mountains, you never have the opportunity to use big power while cranked over. It is all about agility and the ability to transition quickly.
Stability is determined by the relationship between rake and trail. More trail buys you stability, the rear tire contributes only insofar as the sidewall isn't flexing and moving you around. As you bank the bike over, the rear contact patch moves towards the inside of the turn, and the more it has to move the more pressure you have to apply to the bars. Narrow rear tires don't move the contact patch as far inward as with wide tires and they transition easier. That is a choice for street riding. On a track at track speeds, I might make a different choice, but consider that most race bikes take Turn 8 at Willow Springs big track at higher speeds than even my modified K-100Rs is capable of with miles of straight road ahead of it. What am I trying to prove with a mondo wide rear tire?
On my 2007 Street Rod I ditched the stock wheels, 19X3.5 front and 18X5.5 rear for wheels from an XR-1200, 18X3.5 front and 17X5.5 rear to access a wider selection of tires. Even though both rear tires were 180/55 profile, the 17 incher on there now is about 6 or 7 mm narrower than the 18 and it turns in beautifully. It is also dead neutral, meaning once banked over in a sweeper I can put some friction on the thottle lock (stock HD throttle locks are a thing of beauty), take my hands off the bars and the bike will track a corner perfectly. My old K-100RS used to be equally neutral on the stock wheels with Dunlop D205 radials, but once I could no longer find decent radials for those narrow old wheels, I converted the bike to Paralever so I could ues later model wheels. Now, with a 160/60ZR18 on the rear the bike has lost agility it once had, but I can buy radials that fit those wheels. I can live with it I reckon, but the old set up with a 140/80ZR17 rear was more fun on tight roads. My BMW tech friend like to put a 130/70V17 tire on the rear of K-75s to maximize agility.
I had even considered mounting a 160/60ZR18 on the Street Rods original rear rim (you have no idea the difficulty fitting a Sportster style wheel to a V-Rod, getting pulleys, gearing, spacing and belt lengths worked out was a minor engineering adventure as nothing swaps between V-Rods and any other bike made) but the 5.5 rim width is just too wide for a 160 tire.
ISAMEMON
Grammarian no, Rider yes
narrow tires
like a bicycle, are easier to turn and pedal
so the theroy above should be good
but im an old fart, I dont road race, my bike is not a crotch rocket, I dont pedal this old girl
so for me, an old fart in a old mind set, I want as much ground contact as I can get
shucks, I only got two wheels on the ground at 70mph
right or wrong. I will stick with fatties
like a bicycle, are easier to turn and pedal
so the theroy above should be good
but im an old fart, I dont road race, my bike is not a crotch rocket, I dont pedal this old girl
so for me, an old fart in a old mind set, I want as much ground contact as I can get
shucks, I only got two wheels on the ground at 70mph
right or wrong. I will stick with fatties
42906
Themason
Don't let it get around. Next thing will be scooters. lol. I hear they are a lot like fatties, fun but don't let your friends see you.
+1! Horrid tires!
As to original poster, if I had to go metric, I would go 110/90 rear, 100/90 front. Although that rear does make bike sit rather high on sidestand, tire change way easier, no rubbing on swingarm
R
RPG
Guest
Avon RoadRider 3.25 x19 and 4.00 x 18 are all the tire you'll need for that bike. They will fit and the bike will handle wet and dry just fine.
have them on my R90s. Did a 2000 mile Blue Ridge Parkway trip in the spring, followed up by a May Track Day. Three days on the BRP was in pouring rain and had zero issues. And at the track, the bike was pushed pretty hard with no issues either.
Actually thought of wider tires too, but I was so impressed with the performance, that I'm leaving well enough alone.
RPG
have them on my R90s. Did a 2000 mile Blue Ridge Parkway trip in the spring, followed up by a May Track Day. Three days on the BRP was in pouring rain and had zero issues. And at the track, the bike was pushed pretty hard with no issues either.
Actually thought of wider tires too, but I was so impressed with the performance, that I'm leaving well enough alone.
RPG
1074
Active member
Conti Twin tires
Althought they say that these tires were created for the BMW twins, you have to keep in mind that we're talking about 70s technology.
So if you're doing a restoration and want period correct tires, then go ahead and get the Contis. If you're going to ride the bike, then I'd much rather have a modern tire that will last longer, stick to the road better, be much more competent in the rain, and not get as squirrelly on metal grate bridges and rain grooves.
Just a thought!
Althought they say that these tires were created for the BMW twins, you have to keep in mind that we're talking about 70s technology.
So if you're doing a restoration and want period correct tires, then go ahead and get the Contis. If you're going to ride the bike, then I'd much rather have a modern tire that will last longer, stick to the road better, be much more competent in the rain, and not get as squirrelly on metal grate bridges and rain grooves.
Just a thought!
rogermansfield
beemerfield
Anyone had any experience with Heidenau? I have not really looked at them and assume they make a size that will work. If I can get my /5 to be reliable, I will start looking into some new tires.
kwb210
New member
Avon AM26
I have a 1977 R100, ride it 10,000 miles a year, all touring and loaded. I have tried a few differnet brands. I come back to the Avon AM26. last spring I needed a tire sooner than I had planned, returning from Mexico to WA state, so I stopped at a BMW dealer who had a 18 inch tire in stock, you take what they have! It was a Metzler ME88 and I don't care for it, to hard a compound, I would be willing to bet it will last forever but if you like to run a bit hot in corners it is simply to hard and slips or slides a bit on corners, I don't like that! The Avon is probably softer, I still get about 7.500 on a rear if I watch the tire pressure, WAY less if it is under inflated. I check it cold each morning while on a ride, after a couple of days it needs a couple of pounds. But the Avon allows me to run a bit faster in corners. Sometimes a faster corner is planned and then there is the time that you are entering to fast, that is when a softer compound works for me. I run 32 in the front and 38 in the rear, remember, that is a loaded bike. I mistakenly ran a 90/90/19 on the front instead of the 3.25x19, still got about 10,000 miles out of it and never felt a difference. I just changed it out for a 3.25x19 (avon am26) since I am planning on one more 3,500 mile run before the riding season comes to an end, remember, I am just north of Seattle, WA. My comments are simply what works for me and my riding style on a bike that really gets out there. I also have a 1972 slash 5 Toaster Tank, it has 6 year old Metzlers, they work fine on the club rides the bike runs. Anything would be fine, the bike just happened to come with them and at maybe a 1,000 miles a year it does not matter to me.
Kurt
PS: I just realized I need to update my signature line to include the 72 Toaster
I have a 1977 R100, ride it 10,000 miles a year, all touring and loaded. I have tried a few differnet brands. I come back to the Avon AM26. last spring I needed a tire sooner than I had planned, returning from Mexico to WA state, so I stopped at a BMW dealer who had a 18 inch tire in stock, you take what they have! It was a Metzler ME88 and I don't care for it, to hard a compound, I would be willing to bet it will last forever but if you like to run a bit hot in corners it is simply to hard and slips or slides a bit on corners, I don't like that! The Avon is probably softer, I still get about 7.500 on a rear if I watch the tire pressure, WAY less if it is under inflated. I check it cold each morning while on a ride, after a couple of days it needs a couple of pounds. But the Avon allows me to run a bit faster in corners. Sometimes a faster corner is planned and then there is the time that you are entering to fast, that is when a softer compound works for me. I run 32 in the front and 38 in the rear, remember, that is a loaded bike. I mistakenly ran a 90/90/19 on the front instead of the 3.25x19, still got about 10,000 miles out of it and never felt a difference. I just changed it out for a 3.25x19 (avon am26) since I am planning on one more 3,500 mile run before the riding season comes to an end, remember, I am just north of Seattle, WA. My comments are simply what works for me and my riding style on a bike that really gets out there. I also have a 1972 slash 5 Toaster Tank, it has 6 year old Metzlers, they work fine on the club rides the bike runs. Anything would be fine, the bike just happened to come with them and at maybe a 1,000 miles a year it does not matter to me.
Kurt
PS: I just realized I need to update my signature line to include the 72 Toaster
j_withers
New member
My local BMW mechanic can't get the battleaxe BT-45's in the standard sizes (3.25-19 and 4.00-18).
I found the Roadriders in that size.
Searching online isn't yielding much results either yet Bridgestone has them listed on their site. They seem available in the UK but not in the USA.
Does anybody recommend a supplier?
I found the Roadriders in that size.
Searching online isn't yielding much results either yet Bridgestone has them listed on their site. They seem available in the UK but not in the USA.
Does anybody recommend a supplier?
bikerfish1100
New member
google should be able to help you just fine with that.
heres what i came up with- (but work won't let me go to any of these sites)
http://www.bing.com/search?q=bridgestone+tires,+battlax+45&src=IE-SearchBox&Form=IE8SRC&adlt=strict
also, you can do a search within the forum to find previous tire threads where peeps have previously asked the "where's a good place to buy my tires?"
typical popular sources are:
Motorcycle Superstore
Cycle Gear
Tires Unlimited
Southwest Moto
etc etc
j_withers
New member
As i mentioned, i already searched online and I can only find the metric sizes in the US for the BT45.
I can find the Avons and the Continental "Conti-Go!" tires in standard sizes.
If anybody has a source to get the BT45 in the standard size in the US, I'd appreciate it. I fear that it could get very costly though.
I'm starting to lean on getting the Avons (due to size availability) though i have heard the compound is very hard.
I can find the Avons and the Continental "Conti-Go!" tires in standard sizes.
If anybody has a source to get the BT45 in the standard size in the US, I'd appreciate it. I fear that it could get very costly though.
I'm starting to lean on getting the Avons (due to size availability) though i have heard the compound is very hard.
jad01
New member
I've been using the Avon RoadRiders for awhile now and I don't find them particularly hard (relative to Contis or Metzler LazerTecs). They handle well and adhere nicely at a spirited pace in the twisties. I ride two up with my wife pretty frequently, and if memory serves, I got around 7500 to maybe 8000 miles out of the rear (maybe that gives an indication of how hard the compound is?). I'm at about 10,000 miles on the front (but it's getting due for replacement). I've been led to believe that they're popular with the British cafe racers on classic Nortons/Triumphs in my area.
bikerfish1100
New member
sorry- i misunderstood your dilema., and your earlier efforts. i found no success on the BT45s in inch sizes either. there is a near metric equivalent- but i would probably consider Avons over that option, or the new Contis being offered in inch sizes (but NOT the RB2/K112 combo, as those flat out sucked).
good luck.
j_withers
New member
I was looking at the BT45 equivalents and the closest rear seems like the 120/90-18 V rated.
A 4.00x 18 has an OD of 675mm and TW of 117mm
and the 120 has an OD of 673mm and TW of 121mm... which might be why it gets so close to the subframe and is hard to install around the brake shoes.
There seems to be an identical front though based on the few specs they give on their site with a 100/90-19
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