Originally Posted by JayB
Didn't realise there was a difference in headset sizes so am interested in this. What about new steel solos? What size do they use? Are there advantages in larger size?
Available headset sizes include:
1” threaded, aka quill and threadless: The traditional size for all bikes through the 80’s.
1.125” threaded (rare) and threadless: Developed in the late 80’s for mountain bikes.
1.25” threadless, aka, Oversized developed by Fisher in ’89 for it’s Ti fork
1.5” threadless, aka OnePointFive: A new standard for downhill and freeride bikes
1" fork steerer tubes & headsets (with subtle variations) were the norm for just about all bicycles until the late 80's. Up and until Dia Compe patented the threadless fork steerer and Aheadset system in the late 80’s, all forks steerers and headsets were threaded and used cup and cone-type bearing systems (as did most hubs and bottom brackets) that required a certain amount of skill and experience to properly adjust. Tandems merely used what was widely available for standard touring and road bikes which, as you might expect, was often times marginal at best.
The advent and mass appeal of the mountain bike in the 80’s came a ton of development money and new mountain-bike specific technologies and components. In addition to sealed bearings and mountain bike component groups from Sun Tour and Shimano, mountain bike designers at Klein, Yeti, and later Cannondale began to experiment with oversized headtubes and fork steerers as a way of improving the durability and handling of their still rigid mountain bike designs. In 1989 Fisher introduced its 1.25” Evolution headset for use with their titanium fork. Around the same time Yeti was experimenting with 1.125” and Klein had a different size in mind and while I’m unsure who else jumped in when – Cannondale seems like they were an early sign-up – Tioga’s 1.125” (1 1/8”) “Avenger” headset was adopted as a new “standard”. Right on the heels of the new standard Dia Compe’s threadless fork and Aheadset headset was introduced in 1992, a design which greatly simplified fork installation and adjustments and also allowed fork designers to use more lightweight steerers since threaded pipe was no longer required. The tandem builders immediately seized upon the use of just about every mountain bike component to address the inherent weaknesses that traditional road bike components had when used on tandems, to include the larger headsets, wide-range mountain bike gearing & derailleurs, stronger and less expensive hubs with sealed bearings, linear pull (aka, V) brakes, and more robust bottom bracket and crank designs.
So, by the early 90's you could find all three size headsets in use, making life as a bike shop owner or mechanic, never mind a bicycle fabricator, a bit more complex and expensive given that they now had to have tools and parts for all three. Many road bike companies who also built off-road bikes started to adopt the 1.125” threadless headsets as the “standard” for their road bikes to help eliminate some of the variability issues. While it added a little weight, it did make for a more robust design. By the late 90’s I’d guess about ½ of the road bikes were probably using the 1.125” threadless headsets and all of the tandem builders had adopted them as well. As for current road bike offerings, I suspect that the 1" may be more prevalent on high-end or niche brands/models... but can't say for sure what the 1" vs 1.125" market split is. All 3 of our solo bikes have 1" headsets. In fact, I don't think I've ever owned a solo road bike with anything but a 1" headset. Then again, I've never weighed more than 172lbs and tend to hover around 150 lbs - 160 lbs.
There is now a movement to adopt a new 1.5” standard for off-road bikes, with an eye towards the demands of the freeride and downhill market. You can read all about it at this Website: http://www.onepointfivestandard.com/index.asp
Santana, who has always worked to put as many “exclusive” design features and to use what it believes are the most robust materials, designs, and components on its tandems – to include the 1.25” headsets and the controversial 160mm rear spaced drop-out / hub specification that failed to catch on as a standard for tandems. To their credit, Santana makes fine products that are very reliable and enjoys tremendous owner loyalty. Of course, so do all of their major competitors.
As for other tandems and the 1.25” headset, Cannondale followed Santana’s lead with the 1.25” headsets in ’93 – ’95 but shifted to the more common 1.125” in ’96. Bike Friday slipped my mind; they are using the 1.25” headsets and I believe Meridian and Longbikes may have also used them, noting that both of these builders never really got out of the gates. Meridian quitely went out of business in late '03 and Longbike is focused on recumbents but may still build upright tandems to order. Other than that the standard hasn’t caught on. I’m sure there are a few other tandem builders who have used the 1.25” headset intermittently or as an option on a custom bike but, again, it’s just not what I’d call a widely used “standard” except for Santana.