Tire inserts for XC racing

What size backer rod are you using for your Cx wheels? Is there a specific way to size (e.g. internal width minus 2mm, etc?)

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For CX I am using i9 aluminum rims that are 23.5mm internal width and Donnelly MXP 33 (which on those rims measure over 37mm).

I used these 7/8” backer rods that were available at the local hardware store for cheap. image
Have worked well so far.

On The Cycling Podcast “Life in the Peloton” podcast, Mitch Docker did a diary of the first few races. He interviewed one of the EF mechanics, and they said they are using inserts, but couldn’t go into details as it was a competitive advantage. Tweaked my interest, but I haven’t gone further. It was more from Gravel I was interested in them.

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Interesting, I’m sure I listed to this podcast but didn’t catch that they were using inserts. I think it was on the Silca podcast with Andreas Klier (EF director and tech guy) that Andreas said EF had tested and may now be using tubeless tires without sealant.

Yeah, nice, I’ve got 23mm internal width rims and I run MXP/PDX tires, so I may give this a try. Did you try anything like the cushcore gravel.xc insert, or just go straight to DIY? Cushcore says 120g, which is a little nuts if it’s per wheel.

Do you get to do any CX racing this year? Everything around here (greater Seattle area) is canceled.

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Yeah, the mechanic was talking about it. I think he said they brush the tires with sealant to get a good initial air seal but then that’s all they use.

Did not try commercial other than buying one from R2-bike which was too big for my XC wheel/tire combo and I realized that it was just backer rod.

I would like to try one that fits into the rim channel a bit better and is moulded in one piece, but until there are better cost/weight options I’m good with DIY.

The official CX season is cancelled in Western Canada but there will be a few unofficial races - 4-up, 90sec bracket-style elimination tournament and The like.

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Without sealant but with inserts. But if I recall correctly, that was because they’re changing them so frequently, and I would also guess they expect to be able to change out the wheel.

did you just tape the ends together? any idea what the backer rod weighs? might try some in my CX setup too

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Are they closed cell foam? If so that’s not a bad idea. The problem I’ve see with DIY inserts is people using open cell alternatives and it soaks up the sealant.

Cushcore vs. DIY is not comparable. Cushcore does so much more than mere rim protection. There are many comparison vids on youtube check em out. :slightly_smiling_face:

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Yes, the ones I use are closed cell. I’m sure open cell would suck up the sealant immediately. I’m using Gorilla Tape to tie the ends together.

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Tire inserts now being used in the TdF

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Any other long term feedback on the DIY inserts?

I’ve just put some 40mm backer rod into my 29x2.3’s they fits okay - haven’t had the chance to ride it yet though. It seems to take up quite a bit of the volume. I’m wondering if the foam is going to be a bit too firm / maybe in narrower rims to go for more like 30mm rod?

Also wondering if it could have a negative effect on cornering. Just seems like the tyre could end up being more firm when pushing on the side wall?

In two years everyone will use them

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I was thinking dripping my toes in with tubs for CX next year (Southern hemisphere). Should I wait to see where this trend goes?

My experience is better cornering, probably due to being able to drop the pressure 1-2psi.

Long term my only learning is that you need to monitor sealant levels and top up - over the course of a season the closed cell foam will soak up maybe 10g of sealant. Other than that and the (really quite reasonable) weight penalty, it’s all upside.

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You can buy my (and/or my wife’s) Carbon tubulars- I don’t need them anymore.

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I’m trying inserts this year, the advantages of tubulars over inserts would have to be staggering to justify the increase in hassle and decreased flexibility. As far as I know, the trade-offs just aren’t there. For instance, the value of being able to change tire tread day-to-day is huge. If you’re a pro and someone is managing your tubulars for you, it’s a different story, but for the rest of us I bet adapting tread to conditions would lead to more speed.

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FWIW, here is a road insert (only 22 grams).

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