In the first of a series of articles on building a cyclo cross race bike on a budget and shedding weight without compromising performance, we are going to focus on the biggest lumps of steel on a cross bike - the cassette and chain.
A few years ago, cross bikes typically came spec'd with double chainrings, usually 36/46t, and an 11-28t cassette. This gave a huge range of gears for riding off-road.
Fast forward to today and cross bikes are regularly spec'd with a single ring, usually 40t, and to keep a wide range of gears, an 11-32t or 11-36t cassette.
Today's single ring set up with a wide narrow chainring and a clutch mech is a huge improvement in reliability for cross. Yes there is the argument about increased friction and wear from the chain line in 1st and 11th gears but, I have not dropped a chain nor ripped off a mech since I changed over. And losing the shifter internals (on SRAM), cable, front mech and a chainring definitely saves some weight.
But, the 1x simplicity and weight saving has come at a cost...
A SRAM PG-1130 cassette is commonly spec'd on bikes costing up to £3000, the 11-32t version weighs in at 320g and the 11-36t version weighs 427g.
Those who are running the 11-42t cassette are dragging along a huge 545g (SRAM's weights don't include the lock ring).
For context, the 11-28 cassettes of a few years ago weigh in at 277g.
So how to have the benefit of 1x, realise the potential weight saving and keep an appropriate spread of gears for racing?
1. In your week night training and weekend races, check out which gears you are actually using.
2. Use BikeCalc.com to see what the ratios are (or see the table at the bottom of this article).
3. Remember that when racing, below a certain speed, it is faster to run.
In our experience, when you look at the ratios you actually use, and you think about when it's faster to run - then a smaller cassette is a viable option.
4. Compare the gears you use to a 38t or 40t chainring with an 11-28 cassette.
It is very likely that you will have all the gears you need / use in a cross race.
Do bike manufacturers think we've got weaker since 2015 and need easier gears?
Coming back to the 36/46 set up of old, a 36f/28r smallest gear has a ratio of 1.29:1, where as today's 40f/32r has a ratio of 1.25:1, a 40f/36r has a ratio of 1.1:1 and the 40f/42r's ratio is 0.95:1.
At the other end of the cassette, how often are you using your 11t or 12t cogs? I would expect not very often.
If like for me, it makes sense for you to move to an 11/28 cassette, you can make some big weight savings.
11/28 cassette weights & cost;
Shimano 105/SRAM PG1130 - 277g - £35/£39
SRAM PG1170 - 259g - £55
Shimano Ultegra - 246g - £46
(You can use either SRAM or SHIMANO cassettes with both SRAM and SHIMANO groupsets)
Measured in £/g this is a very cost effective way to remove some weight from the back end of your race bike.
The current trend for larger cassettes offers an opportunity to save even more weight, part used 11/28 192g Dura-Ace cassettes are coming up on Ebay and Facebook groups for £35 to £60, but you will have to hunt for them at this price.
Make sure you buy from adverts which state 'good condition' and pay with PayPal (standard advice for buying 2nd hand kit) so you are protected from buying a dud.
Look carefully to see there are no flat spots worn on the teeth, pay particular attention to the steel cogs at the bottom of the cassette.
Cassettes with chain shaped rubs marks on the side of the titanium cogs have not caused me any problems.
If you need to change your chain ring then Absolute Black is a quality product but fairly expensive, Superstar Components' rings are great value and work well (if they are in stock!). Amber-bikes make a very nice ring for Shimano 4 bolt chain sets too.
All three offer oval rings too, but this needs it's own article...
Even better, change the cassette/chainring on your new bike before riding it and sell them "as new" condition to off-set some of the cost.
It might feel like a huge change going to 11/28, but by following the process above and using the gear calculator to make comparisons, you are unlikely to go wrong.
I think that losing 235g off the back end of a £3K Canyon CFSL8 for c.£40 is money well spent!
Cross bike chains have a hard short life. The gritty and dirty environment wears them out pretty quickly.
Changing your chain before it is worn out is very good advice, you'll extend the life of your cassette and chainring if you do, but does upgrading make sense?
The short answer is no.
Whilst there are some improvements in the surface finish/treatment of the higher group set chains, life expectancy does not improve in balance with the extra cost.
The weight saving from the hollow pins and cut out links is marginal; a SRAM Red chain weighs 253g and costs £28 but the one to go for is the SRAM 1130 silver chain, it weighs 266g and costs £16.
It would be better to use the cheaper chain and replace twice as often (especially if you are using Dura-Ace cassettes!).
And I've yet to suffer a snapped chain since I moved to SRAM, which was an annual event with KMC...
To keep your drivetrain smooth here are our recommendations.
When to change a chain?
This article from bikeradar covers the subject nicely and makes a good recommendation for the tool to use. However, 1x chains run the full width of the cassette, so suffer more lateral wear, and gear changes might get slack before the tools says the chain is worn...
Next up - Chainsets
Building a race bike on a budget #2 can be viewed here
Prices quoted are from a very large online retailer.
Gear ratio table (source BikeCalc.com)