Help with new Continental 700x28c tires
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  1. #1
    RoadBikeReview Member
    Join Date
    Oct 2015

    Help with new Continental 700x28c tires

    I am hoping someone can offer some advice or insight re: 700x28c tires.

    I recently purchased a 2013 Lynskey R255. I am thoroughly enjoying this bike and have already put over a 100 miles on it.

    This bike came with:
    Shimano 105 brakes
    FSA Sport CF Fork (36 degree cartridge)
    Shimano R500 622x15c rims

    Continental Ultra Sport Tires 28/622 (700x28c)

    I am 5'10" and weigh about 195lb (down from nearly 250lbs after many years of lifestyle adjustments). Most of my riding is done on long country roads in hill country. The roads are paved, but can be teeth-rattling at times.

    My other bike is a Trek Madone and has 700x23c tires, which work fine, but I have found I prefer the 700x28c tires that the previous owner had put on the Lynskey.

    I wanted to upgrade to a bit more durable 700x28c tire for the type of riding I do, so I purchased a pair of Continental Grand Prix 400s II 700x28c 28/622 tires from a bike shop in CO (via amazon). The reviews I read led me to believe this would be a good tire with a nice balance between performance and durability.

    I started with the front tire. But I ran into a problem when I went to re-mount it. The tire rubbed on the top of the fork and wouldn't spin freely. I would spin slowly and wind to a stop.The culprit definitely seemed to be the bead(s)/seam material left from manufacturing. So I lowered the pressure from 90lb to roughly 75lb, just to see if it'd help with the freespin (I wouldn't ride at that pressure). It didn't help much, so I pulled off all of the tiny plastic 'nubs' with my fingers, which helped slightly. But the remaining tire seam was still clearly rubbing. Rather than attack it with a razor, I tried sanding down the extra seam-rubber with some very fine grit sandpaper.

    Long story short, I made it better after quite a bit of patient sanding, but at full pressure, it still rubs (without my weight on the bike), and of course I can't send the tire back after my custom 'augment'.

    I'm baffled why the same brand and size won't work. I know the specific tire model is different, but still I would think it should work because the labeling shows them to be the exact same size.
    I tried to measure the gaps left between the tires and frame/fork with the old tires on, and have about 2mm in front and 5mm in back. I did not try to change out the back tire, but given that it appears to have a little more room, I am inclined to think it may fit. But even if it does, I don't really want to change that one if I can't put the matching tire on the front.

    Am I missing something embarrassingly simple (which is very likely)? Has anyone out there run into this type of situation before? Perhaps I should give up on new 700x28c tires and go with 700x25c?

    Any advice/help is much appreciated.

  2. #2
    RoadBikeReview Member
    Join Date
    Jul 2011
    The 25mm GP4 sit out closer to 28-9mm FWIW. Especially on wider rims than the old Open Pro Standard.

    Also, anything Michelin 25mm casing is 29mm mounted. I dunno how the bigger than 28 Contis run, and only then the All Seasons which I like for winter, but they are small for a 28 as compared to the two I just mentioned.

    I did just get some 32 Gators given to me last night to try. But not mounted them yet. IIRC the 32 are more true to size. Such as my memory is....

    So more than what size tire you will choose by number. Be clear before plucking down the coin what actual mounted size you want and can fit on you bike would be my strong suggestion.

    EDIT; I just mounted one of the 32mm Gatorskins, on a 15C [open Pro width] it is 29x29.1mm. I'd guess on a 19C wider rim it would be more like a 32 width max, and 27-8mm high. Leaving me with the same impression as the All Seasons being a bit small for the labeled size. I think Conti just does that with their heavier tires so a bigger labeled size justifies the weight as compared to the competition perhaps.

    EDIT, EDIT: I just measure the 32mm Gator on the 15C rim again. It is now 29.5 w x 29mm high. I did not expect it to swell per say being it is used and been on my friends bike all season. Maybe the bead climbed [rode up with wear] a little and let it bloom. ;)
    Last edited by robt57; 10-06-2015 at 12:57 PM.
    Quote Originally Posted by Robt57/Me!
    Everything you read that I post is just '1' guy's opinion, try to sort it all out best you can. ;) I will try to add value in my posts, if I miss the mark please let me know using a little decorum.

  3. #3
    grizzly moderator
    Reputation: dcgriz's Avatar
    Join Date
    Feb 2011
    The stated tire sizing identifies the tire nominal width at a tolerance of +/- 3mm from the actual width. Furthermore, to make things worst, the same tire will measure 1-1.5 mm more in width when fitted on a 17c rim vs. a 15c rim. So you see if a tire starts at +2mm and then installed on a wider rim, then it could easily end up +(3-3.5mm) wider than its stated nominal width.

    Unfortunately, these tolerances do not always follow the same direction. Some manufactures understate their sizes and some overstate them. To make things even more confusing to the consumer, these discrepancies are not just between different manufactures but also between the lines of the same manufacturer.

    Case and point, at least for Continental. The GP 4000S II in 28mm measures a whopping 31mm in width when fitted on a 17c rim. The GP 4 seasons in 28mm starts at 26.8mm when fitted onto the same rim.

    I would advise you not to run a tire that rubs your fork crown. If you like the GP 4000S II then replace the 28mm with a 25mm. The 25mm will measure around 27-28mm on your rims.

  4. #4
    RoadBikeReview Member
    Join Date
    Oct 2015
    I wonder if the same people who write our tax laws also wrote the book on tire sizing? I will give the 25mm tires a try and report back. Thank you both for your help!!

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