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Thread: Radial tires on vintage bikes - Continental etc

  1. #1
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    Default Radial tires on vintage bikes - Continental etc

    I'd seen several years ago that Continental had developed the Classic Attack radial tires specifically in GS/KZ/CB etc skinny 18" & 19" sizes...




    I've been very happily running fast wearing ultra-gripping Shinko 18" bias ply / cross ply tires for years on my friends' stock GS rims AND my 2.50-18 / 3.50-18 aftermarket D.I.D. & Sun wire spoke rims.
    The last long ride on my Shinkos to visit my parents, I remember ripping it on backroads and being reminded of how much I loved the grip of these Shinko tires. Chuck Sr. pointed out that my tread depth was getting low for me taking off on a 10 day trip of mountain riding and camping all the way to Barber Vintage Motorcycle Festival in Alabama...
    I figured what the heck, Shinko doesn't make a 130/80-18 (which fits a 3.50-18 rim on a GS-four the best), they only offer a taller 130/90-18 & sporty/wider 140/70-18,
    So I figured I'd run some Pirelli Sport Demons this time around,even grippier than the beloved fast wearing Shinkos.
    Pirelli = Out of stock until 2022...

    I scrape the stator cover before I can get the 140/70 Shinko SR714 (on a 3.50 rim) to the edge of the tread. 130/80-18 is best on a 3.50 for the width of a GS750 & larger engine & it's cornering clearance, 130/90 is a bit tall and less sporty due to high sidewall but it'd work (Shinko 230 or 712).

    Well... In searching for "130/80-18" tires, I found that the newest Continental Road Attack tires do come in these sizes!

    So I dropped $290-ish on 130/80-18 & 100/90-18 RoadAttack3 radials...

    First impressions. Rear is very sporty in profile, more of a V-shape vs smooth arcing radius tread profile. This gives far more contact patch leaned over vs upright.
    The front seemed pretty narrow for a 100/90. Measures skinnier than same size Shinko, while the rear measures a very healthy & impressive width.
    Rear is a refinement of a dual compound tire. It uses one rubber compound throughout so no transition between harder center tread rubber and softer sides, they cure the tire very carefully controlling the temperatures in middle vs sides, to allow portions to cure longer vs shorter, achieving a gradual durometer change for ultra soft sticky sides and longer wearing harder center.
    First test rides, I noticed slightly less rear braking power before locking up while riding upright / not leaned over, a result of less upright traction on the rear vs my beloved Shinkos because of the sport cornering focused tread profile shape.
    I tried to break loose the front on hard upright braking, only once on wet leafy pavement did I ever succeed.

    Long 10 day road trip shows very little treadwear on the center of the rear, sides of tread look like a race bike tire or pencil eraser shavings...I was cookin' 'em pretty good pushing it in the mountain twisties.

    It was a very wet road trip, we missed Tail of the Dragon completely due to torrential tropical storm rains while watching the radar on the Deal's Gap Motorcycle Resort WiFi... Rode most of Hellbender 28 before the torrents broke loose, however! Last 5 miles after the bridge/river & massive cliff faces turn on Rt 28, we got SOAKED...

    I ripped most of the Cherohala Skyway pretty hard in the curves aside from the most wet/leafy/shaded areas. Ripped VA-16 Back of the Dragon 33 mile 3-mountain pass ultra tight twisty stretch real good, as well as US-421 the Snake, and portions of the Blue Ridge Parkway. US-58 the Mighty Python was wet and leafy both days but I got down a fair bit in some areas. That road is soooo nice & perfectly flowing but good & tight. Great link between WV-16/VA-16 Back of the Dragon, to Mt Rogers and then south out of Damascus VA into East TN to US421 "The Snake."
    Tennessee 32, the tightest twisty road in the USA, was too tight to run hard for being wet leafy pavement. Many turns are so tight that the pavement stripe painting trucks couldn't make the radius and had to back up and paint an overlapping set of double center lines at the apex of many curves...lol
    I've ridden it in the dry before, and most areas it's tough to hit 40-45mph in the short straights in between curves without race pace acceleration, and at that, hitting it real hard means 25-35mph top cornering speed blazing in the tight curves...until I looked at my speedo a few years back,I felt like I was doing 15mph ripping the tightest curves on TN-32, but speedo read 23-27mph when I did dare to take my eyes off the road for a split second to glance at my speedo...


    These RoadAttack3 "Sport Touring" radials definitely check all the boxes for me to qualify as more sport than touring... The harder cured rear center tread rubber is the only thing "touring" about these tires.

    I'm very pleased...

    The Classic Attack radials get similar reviews although I don't believe they have the same harder cured center strip on the rear tread.



    I dropped down to 18" front from 19" ages ago, & put on longer rear shocks, so my rake and trail have been steepened a bit for more aggressive cornering.
    Going to these radials, the slight headshake that was caused by the quickened steering (only happens when I'd take hands off handlebars between 43-51mph on a 110/90-18 & 35-47mph on a 100/90-18), this was completely eliminated!

    The radial carcass I noticed had very different tendencies vs bias ply or cross ply while I was mounting them. The rigidity is different, and they dont spring back as fast when deformed?
    Cornering seemed to show me that they had a better compliance to the road surfaces, and perhaps a slightly smoother ride.




    The only negative was at 85-95mph (on a closed course, of course!), while riding perpendicular to the prevailing winds I believe, & with fully stuffed Nelson-Rigg saddlebags, the drafts / air turbulence from semi trucks and large trucks occasionally induced a bit of annoying weave where the bike would undulate very slightly left and right rapidly for several seconds.
    I was screwing with the back wheel alignment/chain tension mid trip and thought my gearbox (f'd shift forks) noise was possibly caused by chain misalignment, so I centered the rear wheel via chain adjusters by sighting the rear sprocket to the front. This may have put my tire slightly out of parallel, which could've caused this issue, but it also could be due to the carcass' radial construction vs GS750 un-braced frame rigidity, as well as the very skinny rear center tread contact patch with the bike upright, vs the front (34psi may've been too much for me@ 150lbs + luggage/gear, but I'd read to run a few psi more in radials so I was). Same wiggle tgat a GS550 gives on long 65mph sweepers leaned over hitting bumps or dips, which on a 550 is caused by the lack of two short pieces of tubing bracing the center spine of the frame behind the ignition coils. The 750 has braces there from the factory, but this was definitely some sort of frame flex springing back and forth issue caused by significant wind turbulence whipping the bike around, although my rear wheel alignment might have been cocked slightly sideways and also causing this, as I have had the bike up to very significantly high speeds (in test environments!) with bias supply tires and never had this issue, nor did I on the trip down but was not going as fast as it was mostly back roads.
    Front to rear tires have to have a certain size relationship to handle properly. When you see retro bobbers/cruisers etc with similar / same size fat tires front and rear, this is a mismatch and not conducive to good sporty handling...the skinny upright contact patch of the nice & wide 130/80-18 may've been partly to blame? I should note that I didn't experience this on the first longer portions if the trip mostly on 2-lanes, only the interstate blast 600 miles directly home yesterday, and that was AFTER I was messing with chainline alignment vs rear wheel centering...
    Could be a combination of all of the above including modern radial tires on a 1977 GS frame without the typical "OSS" performance bracing being added.
    Last edited by Chuck78; 10-12-2021 at 01:08 PM.

    '77 GS750
    920cc, 4-1, 1100E swingarm, 18"rims, Fox Shox, twinpot dual disc, VM29, Yosh cams
    '97&'99 Kawasaki KDX220R's rugged terrain rippers
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 trail beast, ported cyl, RM250C head, Lectron carb?, Fox/RaceTech suspension
    '76 Rickman CR GS1000-1100cc roadracer, Yoshi cams&4-1, RF900R fork, Works Shox
    '77 GS400 489cc, GR650 cams, GS500 fork/brake, DID rims, 1100E swingarm, Fox Shox
    '77 GS550 650-740cc
    '78 GS1000C 1100cc, mods
    '79 GS425 bigbore?

  2. #2
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    Overall, I was HIGHLY impressed with these Conti RoadAttack3 radials... I would buy them again if they last 7500+ miles on the rear vs my ultra sticky Shinko rubber which lasts me 4000 rear 8000 front under pretty extreme and aggressive riding conditions on a modified bike.
    The Shinko beats the Battlax BT45V & newer version BT46V although the dual compound rear on the Battlax was longer wearing (5000+ miles) & retains its curved radiused profile much better with wear vs the Shinko wearing a flat spot on commuter/highway use by 3700 miles.
    The Avon AM26 RoadRider people swear by, but they don't cut it for me unless looking for longer wearing tendencies. And they do not age well. I could break the back loose on an almost brand new, new-to-me 100 mile treadwear used 3-yr old tire very easily, and the front AM26 stepped out on me on the Blue Ridge Parkway and one other time...
    So that's there for comparison sake.
    Last edited by Chuck78; 10-11-2021 at 09:50 PM.

    '77 GS750
    920cc, 4-1, 1100E swingarm, 18"rims, Fox Shox, twinpot dual disc, VM29, Yosh cams
    '97&'99 Kawasaki KDX220R's rugged terrain rippers
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 trail beast, ported cyl, RM250C head, Lectron carb?, Fox/RaceTech suspension
    '76 Rickman CR GS1000-1100cc roadracer, Yoshi cams&4-1, RF900R fork, Works Shox
    '77 GS400 489cc, GR650 cams, GS500 fork/brake, DID rims, 1100E swingarm, Fox Shox
    '77 GS550 650-740cc
    '78 GS1000C 1100cc, mods
    '79 GS425 bigbore?

  3. #3
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    Well you're a thoughtful builder and rider so I can't tell you anything much, accept what about proper rim widths?
    Radials need a wider rim than bias ply to work properly.
    I refer to the Bridgestone web site for the recommended rim widths for radials.
    "Only fe' collected the old way, has any value." from His Majesty O'Keefe (1954 film)
    1982 GS1100G- road bike, body, seat and suspension modded
    1990 GSX750F-(1127cc '92 GSXR engine) track bike, much re-engineered
    1987 Honda CBR600F Hurricane; hooligan bike, restored

  4. #4
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    I've run the odd 130/80-R17 on the rear, and currently running a Metzler radial there. The old GS geometry seems to suit them quite well.
    Of course, the darkside tyre beat the pants off them all.
    ---- Dave
    79 GS850N - Might be a trike soon.
    80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
    79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
    92 XJ900F - Fairly Stock, for now.

    Only a dog knows why a motorcyclist sticks his head out of a car window

  5. #5
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    Quote Originally Posted by Grimly View Post
    I've run the odd 130/80-R17 on the rear, and currently running a Metzler radial there. The old GS geometry seems to suit them quite well.
    Of course, the darkside tyre beat the pants off them all.
    Can't comfortably scrape the pegs and stator cover on a darksider!!! And you can't get ultra sticky high performance rubber compounds in skinny 18" darksiders!

    '77 GS750
    920cc, 4-1, 1100E swingarm, 18"rims, Fox Shox, twinpot dual disc, VM29, Yosh cams
    '97&'99 Kawasaki KDX220R's rugged terrain rippers
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 trail beast, ported cyl, RM250C head, Lectron carb?, Fox/RaceTech suspension
    '76 Rickman CR GS1000-1100cc roadracer, Yoshi cams&4-1, RF900R fork, Works Shox
    '77 GS400 489cc, GR650 cams, GS500 fork/brake, DID rims, 1100E swingarm, Fox Shox
    '77 GS550 650-740cc
    '78 GS1000C 1100cc, mods
    '79 GS425 bigbore?

  6. #6
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    Aug 2012
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    Quote Originally Posted by Buffalo Bill View Post
    Well you're a thoughtful builder and rider so I can't tell you anything much, accept what about proper rim widths?
    Radials need a wider rim than bias ply to work properly.
    I refer to the Bridgestone web site for the recommended rim widths for radials.
    I'm a stickler for proper rim widths vs tire sizes... As mentioned above.
    The Continental Classic Attack radials were designed for the stock 1.85-19 & 2.15-18 / 2.50-18 rims on our GS's.

    I'm running the newer Continental RoadAttack3 radials on 3.50-18 & 2.50-18 D.I.D. aftermarket alloy wire spoke rims, with properly matched 100/90-18 & 130/80-18 tires, which are a PERFECT FIT on these rim sizes for a GS750/1000/1100 width engine and ground/cornering clearance. I can use the entire tread width edge to edge as I approach scraping the pegs & stator...
    Last edited by Chuck78; 10-11-2021 at 10:22 PM.

    '77 GS750
    920cc, 4-1, 1100E swingarm, 18"rims, Fox Shox, twinpot dual disc, VM29, Yosh cams
    '97&'99 Kawasaki KDX220R's rugged terrain rippers
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 trail beast, ported cyl, RM250C head, Lectron carb?, Fox/RaceTech suspension
    '76 Rickman CR GS1000-1100cc roadracer, Yoshi cams&4-1, RF900R fork, Works Shox
    '77 GS400 489cc, GR650 cams, GS500 fork/brake, DID rims, 1100E swingarm, Fox Shox
    '77 GS550 650-740cc
    '78 GS1000C 1100cc, mods
    '79 GS425 bigbore?

  7. #7
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    Aug 2012
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    On my Rickman CR1000 build with a GS1000-1100cc engine, I've always planned on running Bridgestone Battlax BT-016 Pro radials which are a higher performance version of these Conti RoadAttack3 radials basically, even down to the peakey profile to give quick turn-ins + more contact patch leaned over vs upright...

    The BT-016 Pro radials only come in 110/80-18 & 150/70-18 (in the range we'd need for a 1980's retro superbike) which requires a 4.00/4.50-18 rear rim to properly run. I hunted down such set of 40h Akront TR rims for the Rickman hubs specifically! 2.50-18 front, 4.25-18 rear!

    https://www.bridgestone.com/products.../detail/pr008/
    Last edited by Chuck78; 10-11-2021 at 10:06 PM.

    '77 GS750
    920cc, 4-1, 1100E swingarm, 18"rims, Fox Shox, twinpot dual disc, VM29, Yosh cams
    '97&'99 Kawasaki KDX220R's rugged terrain rippers
    '74 Rickman VR250MX
    PROJECTS:
    '77 Suzuki PE250 trail beast, ported cyl, RM250C head, Lectron carb?, Fox/RaceTech suspension
    '76 Rickman CR GS1000-1100cc roadracer, Yoshi cams&4-1, RF900R fork, Works Shox
    '77 GS400 489cc, GR650 cams, GS500 fork/brake, DID rims, 1100E swingarm, Fox Shox
    '77 GS550 650-740cc
    '78 GS1000C 1100cc, mods
    '79 GS425 bigbore?

  8. #8
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    Quote Originally Posted by Chuck78 View Post
    The only negative was at 85-95mph (on a closed course, of course!), while riding perpendicular to the prevailing winds I believe, & with fully stuffed Nelson-Rigg saddlebags, the drafts / air turbulence from semi trucks and large trucks occasionally induced a bit of annoying weave where the bike would undulate very slightly left and right rapidly for several seconds. ...
    Pray tell, ... just what were those trucks doing on that "closed course"?

  9. #9
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    Quote Originally Posted by Chuck78 View Post
    Can't comfortably scrape the pegs and stator cover on a darksider!!! And you can't get ultra sticky high performance rubber compounds in skinny 18" darksiders!
    On a 135R15 darksider I can if I want to - but the rear is admittedly a bit lower than stock.
    Only drawback is the higher gear ratio resulting from it. That's why it's currently off the bike.
    I shall be revisiting it with a 165 Michelin once I get my lathe in operation to make some longer hub drive pegs.
    However, I don't normally drag pegs and engine bars on my normal routes around here, as you never know what's around the corner. Been caught out like that too many times.
    ---- Dave
    79 GS850N - Might be a trike soon.
    80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
    79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
    92 XJ900F - Fairly Stock, for now.

    Only a dog knows why a motorcyclist sticks his head out of a car window

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