CYCLINGFORUM.COM - Where Cyclists Talk Tech --- Return To Home

 

    Register FAQ'sSearchProfileLog In / Log Out

 

****

cyclingforum.com ****

HOMECLUBS | SPONSORS | FEATURESPHOTO GALLERYTTF DONORS | SHOP FOR GEAR

Return to CyclingForum Home Page CYCLING TECH TALK FORUM
          View posts since last visit

How fat is too fat?
 

Author Thread Post new topic Reply to topic
Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

8/24/19 11:11 AM

How fat is too fat?

I mean for road rides. ;)

I tried to out sprint a friend on his Roubaix with smaller road tires at the end of 35 pushy miles yesterday.

I got to a point where the tires/wheels just would not accelerate additionally. And at a lot lower cadence than usually observed with go fast 'road' setup. Needless to say James went by.

Was running disc 32 spoke wheels with 38mm Soma Supple Vitesse EX. EX is the non SL, I went for wear over lighter mass for these. Tires are reasonably light @ 320gr. tubes 83 gr, which I do not believe frankly, but did not weigh them.

45/55 PSI for a comfort test for the ride. I suspect this made matter worse as the mush upon each thrust was quite noticeable.

Now while not 'road' optimum on the aggressive side of riding/things. I was quite surprised how well it worked overall. Perhaps more air next time around.

My other fat tire setup is smooth tread 42mm Maxis Refuse tubeless on +125 gram ea. heavier rims. Now those on a solo 30 mile ride wear you out starting about 25 miles unless you are dogging it.

Yada

Anyway, my position [after a season or 2 tinkering] re:fatter tires for 'go fast riding' is that there is diminishing return after 28-30mm. But how much 'go fast' happens on rides for old farts on average as compared to say 20 years back....


EDIT: some additional googling seem to show the tubes are actually lighter than claimed. But 29/38mm tube size that light in my mind I have a hard time absorbing. ;) To be clear I am referring to the Challenge S.C. Latex Tube 700x29/38 size.

 Reply to topic     Send e-mail

dddd
Joined: 11 Jan 2004
Posts: 3280
Location: NorCal

8/24/19 2:03 PM

I'm running the rather light (at 320g for an actual 34mm wide tubeless tire) pair of Mavic Allroad Elite tires on my 'cross bike, these have a rather smooth tread and I'm running them at 50-55psi. They seem to roll well but the bike doesn't feel fast when I exert intense pedaling efforts.

It's known that as tire width exceeds roughly 28mm that the bigger tires will slow the bike down.
Also, from the most recent tests on bicyclerollingresistance.com, when different-width tires are adjusted to similar "drop" or "comfort level", rolling resistance is actually higher for the >23mm tires unless the road is rough. This contradicts the previous results of tests performed with different sizes (widths) of tires inflated to the same pressure.

So, combining the aerodynamic and rolling resistance losses of wider tires, these are slower even before we figure in any added weight or added sealant-sloshing losses.
And the rolling resistance of heavier tires, (thicker, or with more belting, or having a cheaper casing) are also more seriously affected by the sort of pressure reductions that people normally use in their wider tires, since their flexural/hysteretic losses are higher.

So it looks like we can almost assuredly predict that the next on-road riding fad will be a return to the 19 and 20mm tires fit onto "skinny" rims in frames featuring fag-paper clearances around the tires.
I think that the pro peloton has known much of this for a long time and has largely settled on roughly 25mm tires on rims that are aerodynamically optimized for 23-25mm tires.

 Reply to topic    

dfcas
Joined: 11 Jan 2004
Posts: 2615
Location: hillbilly heaven

8/24/19 3:56 PM

I tried 2 different sets of 32's and i don't remember what they were, but they both felt sluggish compared to the 28-29's i normally run. I went back to the 28 Shwalbes which measure 29 on my rims. Thats my fat limit for the conditions I ride, but i don't ride anything rough these days.

 Reply to topic     Send e-mail

Brian Nystrom
Joined: 26 Jan 2004
Posts: 4530
Location: Nashua, NH

8/24/19 4:23 PM

There's obviously a point of diminishing returns, which is probably in the 28-30mm range you mentioned. I've recently run 35mm slicks on my gravel rig for use on the road and they didn't feel too bad, but they were definitely sluggish compared to the 25s I use on my road bikes. Of course, they were very comfortable, so it's a matter of what your priorities are. I certainly wouldn't choose the fat rubber for a group ride.

 Reply to topic    

Nick Payne
Joined: 10 Jan 2004
Posts: 2449
Location: Canberra, Australia

8/25/19 12:06 AM

I take my Open UPPER out on groups road rides without problems in keeping up. It's running Compass Bon Jon Pass 700x35 tubeless, which actually measure 36mm on my rims. I'm running them tubeless at 40/60psi front/rear: with the lightweight casing the tyres weigh ~300g (plus another 50g or so for sealant).

I'd say that on our rough chip-seal roads around here, the gain with the fatter tyre from not being bounced around so much pretty much offsets any increase in rolling resistance.

 Reply to topic    

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

8/25/19 1:06 AM

The only time on the ride I felt like any hold back was happening was when I tried to spin them up past 30mph. The entire ride was the normal fast-ish JRA pace and all was fine, comfort was VG. But the ProCX Lynskey is quite stout, tires did not hide that.


If I take it out again for similar ride I may up tire PSI +15 per wheel and see if a difference...

 Reply to topic     Send e-mail

Anthony Smith
Joined: 12 Jan 2004
Posts: 843
Location: Ohio

9/8/19 8:40 AM

Well another opinoin

I train on 23mm clinchers (going to have to go to 25s as these wear out due to availability) on aluminum rims and race on 22mm (and some 23s again due to availability) tubs glued to carbon rims.

Fads (like fat tires) are just there to sell product and make what you have obsolete so as to sell newer product and have you replace what you have.

They wear well, roll fast and grip well in all conditions (yes even in the rain)

 Reply to topic    

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

9/8/19 12:47 PM

@ 203lb, for road I am currently fin with 27-28mm measured. The Domane team are 28mm GP4 which are 30.8mm @ 90 PSI. I have started trying them @ 75-80. That bike could fit a 32 tire, but I don't see the point of it. Also did a few Domane rides with the 28mm Sectors setup tubeless. I seem to like the 28mm Contis better.

 Reply to topic     Send e-mail

Brian Nystrom
Joined: 26 Jan 2004
Posts: 4530
Location: Nashua, NH

9/8/19 3:54 PM

Sorry Anthony, but it's not a fad. It's actually a case of science debunking conventional wisdom, which apparently wasn't all that wise. In fairness, previous generations of wider tires were not performance-oriented, so it's not surprising that it took a while for these discoveries to come to light. However, now that we know that wider rubber offers rolling resistance advantages on typical road surfaces, aero advantages when coupled with the proper rim, plus reduced fatigue across the board, there's no going back.

RESISTANCE IS FUTILE ;-)

 Reply to topic    

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

9/8/19 4:13 PM

Is it quantifiable anyway? Is the aero negative effect = to CRR gained? [lost?]

I don't really care. I only know to my 200lb girth I am getting a lot better ride, a lot less flats, and longer wear. Having a bigger contact patch may be more of a benefit for a Clyde.

But I have been on 25mm for quite a while now, 5+ years I suppose. And some 27s for as long as it took to wear thru some 27mm Paves, which took a lot less time to wear thru than I would have liked for the cost. I imaging 35ish lb lighter now I might see more miles outta them, but stopped buying them a few years back.

Last Pair of new 25mm paves that were on the wall went on the Look 585, and what a cushy ride it is @ 75/80 PSI. ;) And CRR tests of the day show those no where near the top as far as low CRR goes. I still like the feel of them...

Brain makes the point also. All those fatties of yesteryear were Paselas and heavier. Who made a 32mm tire that was less than even double the weight of most 23mm tires?

Then we got GranPrix-4000ii in 28mm, and a generous 28mm at that. The GP5K I think I saw has 32mm. Betting the same size as the GP4k 28mm off the cuff guess...

Anyone running GP5Ks yet? Are they running generous size like the GP4K had??


Last edited by Sparky on 9/8/19 5:34 PM; edited 1 time in total

 Reply to topic     Send e-mail

dan emery
Joined: 11 Jan 2004
Posts: 6294
Location: Maine

9/8/19 5:32 PM

Data point

IMO the Rene Herse Stampede Pass Extralight 32s (probably slightly less) I recently put on the RSL are fabulous. They are advertised as 254 g (require a tube). The extra lightness is the casing, making that version somewhat more susceptible to sidewall cuts than the standard casing (according to the advertising), but I almost never have sidewall issues. I am riding at 65/70 (195-200 lbs). They have an absolutely silky ride, eat up bumps, and donít seem slow at all. I donít race, never sprint and seldom get out of the saddle, so I canít comment on those activities, but I wouldnít expect any issues. Not cheap. Remind me a bit of seta del mondos.

 Reply to topic    

KerryIrons
Joined: 12 Jan 2004
Posts: 3002
Location: Midland, MI

9/9/19 10:16 AM

The science

Wider tires wear better, are more comfortable, and give better traction all else equal. If the wider tire has a supple casing, it will have about the same total rolling resistance as a narrower tire at a higher pressure. This is because while hysteresis losses (casing and tread flexing) are higher in a wider tire, suspension losses (the bouncing off road imperfections) are lower due to the lower pressure.

Tire wear is not really a function of rider weight, but rather rider power. Tires wear due to the scrubbing action caused by power transmission between the road and tire. This can be from braking or pedaling forces. A larger contact patch means less power per unit area of rubber in contact with the road, and therefore less scrubbing force per unit area to wear off the rubber. If a heavier rider is more powerful, their tires will wear faster. If they are old and weak like me, their tires will last a long time.

Front tires, which do not dissipate essentially any energy except for braking, will last many thousands of miles without losing any rubber. I put over 6,000 miles on a front tire and it lost about 1 gm (scale accuracy/repeatability?) in that time. I wore out two rear tires (casing threads just starting to show) in those 6,000 miles.

 Reply to topic    

Kramer
Joined: 12 Jan 2004
Posts: 111
Location: Richmond, VA

9/9/19 1:11 PM

I read that 32 is the said tipping point

I read a review of the new Trek Domane and it was mentioned in the review that bigger (wider) than 32 and the aero impact becomes too large to overlook.

 Reply to topic    

dddd
Joined: 11 Jan 2004
Posts: 3280
Location: NorCal

9/9/19 10:19 PM

It's funny that online and magazine reviews pretend to be objective, but suddenly when reviewing a bike with 32mm tires they imply that 32mm tires won't slow you down(?).
Not that the difference is huge, at least if the rim is really optimized for the fat rubber, but I've heard that 28mm was the max that had a chance in competition up till now, and that 25mm was faster all around, as evidenced by what the RR teams are using.

 Reply to topic    

greglepore
Joined: 10 Jan 2004
Posts: 1670
Location: SE Pa, USA

9/10/19 6:31 PM

I draw the limit at 28 mm Vlandeerens for the road. I have 42's on the gravel bike, and while they'll get me to the gravel, I don't like to ride them on asphalt. Even the 28 steer slow, but I'll trade that off for the extra traction in the corners and the comfort.

 Reply to topic     Send e-mail

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

9/10/19 7:42 PM

Anyone else still doing tubulars?

 Reply to topic     Send e-mail

Brian Nystrom
Joined: 26 Jan 2004
Posts: 4530
Location: Nashua, NH

9/11/19 4:55 AM

I still have a bunch of tubular wheels, but haven't ridden any of them in years. I've got a lot of NOS tires and rims that I'm trying to sell.
https://nh.craigslist.org/bop/d/nashua-tubular-rims-and-tires-nos/6968804665.html

 Reply to topic    

KerryIrons
Joined: 12 Jan 2004
Posts: 3002
Location: Midland, MI

9/11/19 8:53 AM

Tubulars

I got out of tubulars in 1998 after riding them for nearly 30 seasons. I never looked back.

 Reply to topic    

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

9/11/19 9:34 AM

I sold all my sewup wares in 2015 wit the Nago Victory. The frameset came home n 2018, but thankfully the tubular stuff did not.

My last sewup ride was the 72 Paramount, a glass chunk in a new tire about 10 miles into the ride. I had used sealant so I'd not get flats to make it worth it. ;)

Each time I got about 55 PSI pumping back up the little sealant plug in the hole pooed out. Put on a second pre-glued spare, walked over to to a dumpster and tossed in the one I took off, last ride on tubulars..

 Reply to topic     Send e-mail

dan emery
Joined: 11 Jan 2004
Posts: 6294
Location: Maine

9/16/19 9:14 AM

tests

Here is a blog from Jan Heine summarizing recent tire tests by Tour magazine and Schwalbe. The relatively wide Rene Herse (formerly Compass, which is what appears in the tests) tires do pretty well.

I've noted that on my road bike I am riding the 32mm RH Stampede Pass ultralights, which I love.

No evaluation made by me of test protocol, accuracy, etc.

https://janheine.wordpress.com/?utm_source=Retail+Customer+Newsletter&utm_campaign=a4c71236ef-EMAIL_CAMPAIGN_2017_11_29_COPY_01&utm_medium=email&utm_term=0_f74fbd5ca8-a4c71236ef-108703741&mc_cid=a4c71236ef&mc_eid=1124689c2b


Also, note Jan riding PBP in his Dromartis!

 Reply to topic    

Sparky
Joined: 08 Dec 2003
Posts: 17510
Location: Portland, OR

9/16/19 10:20 AM

Barlow Pass and called it ďalmost as nice as flying."

I am trying out some WTB Horizon 47x650b, cush, but not mush, I like the feel.
I'd like to try something similar in a 38x650b, for less weight to keep spinning. Just not tall enough for anything I have to ride.

The soma supple vitesse feel really floaty, in 38x700 with latex tubes. But as I commented earlier, trying to spin them up where you can spin a 25 I can't get to happen anymore. ;) I did get the EX, which has more tread/weight/wear. I can't see paying more for the ones that wear fast for more supple in that size.

Tubeless Hutch Overrides are on my fendered bike, got a 35mm so no tight fits on the flaps. They are about a 33.8 inflated on a wide disc rim. Read that the 38 is more like a 36. So these are my wet/winter tires.

I pulled the disc off the front Strong Override to see if it would clear the Domane Classics Ed team front, it just touches caliper. did not try the rear. So a real 32-3mm measured is about what that bike will fit. 30mm seem the sweet spot on it.

 Reply to topic     Send e-mail

sanrensho
Joined: 20 Feb 2004
Posts: 826
Location: North Vancouver

9/16/19 10:57 AM

Although I've been riding a lot less lately, I switched to tubulars three years ago on my main bike and couldn't be happier. I have yet to flat though.

Vittoria Corsa CX 25c front, Veloflex Carbon 23c rear (that came with the wheelset). I'll be switching to a 25c rear when the current tire wears out.

 Reply to topic    


Return to CyclingForum Home Page CYCLING TECH TALK FORUM
           View New Threads Since My Last Visit VIEW THREADS SINCE MY LAST VISIT
           Start a New Thread

 Display posts from previous:   


  
Last Thread | Next Thread  >  

  
  

 


If you enjoy this site, please consider pledging your support

cyclingforum.com - where cyclists talk tech
Cycling TTF Rides Throughout The World

Cyclingforum is powered by SYNCRONICITY.NET in Denver, Colorado -

Powered by phpBB: Copyright 2006 phpBB Group | Custom phpCF Template by Syncronicity