What is a Tom Thumb bit?

Horse Illustrated's bit guide describes it as a simple single-jointed mouthpiece paired with the shanks and chin strap of a curb bit, built to keep a snaffle's action while adding a curb's leverage and the idea of neck reining. It is most often described as a Western bit, and the name also shows up on English pelhams.

I ride both English and Western, and the thing I have learned to do with any bit is ignore the name and look at the parts. The name on this one is a good example. It sounds friendly. What does the bit actually do? That is what this page is about.

We report what extension specialists, trainers and the makers say, because they do not all describe it the same way. We do not rank it as gentle or harsh in our own voice. Riders, trainers and a horse's own response decide that.

EquiSearch's bit gallery says the shanks make the Tom Thumb a leverage, or curb, bit despite its snaffle-style mouthpiece, and that the broken mouthpiece acts like a nutcracker on the tongue and bars. It calls the combination a double whammy that can be severe in inexperienced hands.

University of Georgia Extension explains the curb part in general terms. In a curb bit the reins attach to a shank, so pulling puts pressure on the mouth, the chin and the poll. The setting of the curb strap changes how much poll pressure you get. Shank length and shape change severity: longer shanks give more leverage but act more slowly, and straight shanks act more quickly than curved ones. How much leverage you get depends on the ratio of the shank below the mouthpiece to the length above it.

Makers use the same language. The Toklat listing for its chrome-plated copper Tom Thumb says the shanks act with leverage on the poll and the single joint creates a nutcracker action on the soft palate. Shires says nearly the same on its western Tom Thumb with copper.

Trainer and clinician Julie Goodnight writes that it is often mistaken for a mild snaffle because of the joint, and that it is sometimes called a Western snaffle. She says a snaffle is a direct-pressure bit, while a leverage bit has shanks and a curb strap with the reins attached below the mouthpiece. Horse Illustrated says much the same: the bit is often perceived as mild, but it works with leverage.

That is the useful distinction, whatever you decide about the bit. A snaffle's rein attaches at the mouthpiece. That is how the sources define the two families, not a ruling on any one bit. You can read more on that split in our snaffle, pelham, gag or hackamore page.

Tom Thumb can also be a family name rather than one design. Our listings carry Tom Thumb pelhams for English riding, and Shires lists one with sliding cheeks and a multi-link mouthpiece that it says has a mild gag action. When you see Tom Thumb in a title, read the cheek and mouthpiece description before you assume anything.

The table puts the makers' own wording side by side. These are sellers' descriptions, so treat them as the maker's account of its design, not independent testing.

Note how much the shank does. The Argentine style has longer curved shanks and a snaffle ring for a second set of reins, which fits UGA's point that longer, curved shanks act more slowly. The curved pelham version has a shorter shank, which its maker says gives milder leverage.

Horse Illustrated says it is sometimes called a colt-breaking or training bit and is often seen as that step. It also warns that a green horse can be confused, because the change from a snaffle's direct rein to leverage is abrupt.

Julie Goodnight's view, in a 2014 reader-question column, is that no bit fixes a training problem and that moving to a harsher bit tends to increase a horse's anxiety. She also writes that a harsh bit can be mild in skilled hands and a mild bit harsh in poor ones. For a rider who wants a softer feel, she suggests working with a mild snaffle in two hands at home, a reining-style jointed bit with a tube across the joint, or a regular curb with a mild port, which she calls far milder than a Tom Thumb.

That is one trainer's opinion, and makers' wording varies, so take it as a view to discuss with your own trainer. Trainers who ride your discipline and see your horse are better placed than a web page.

University of Georgia Extension's Bits 101 bulletin, reviewed in 2024, concludes that the rider's hands matter most and that many perceived bit problems are really training problems. It also says a poorly matched bit can cause resistance, head shaking or overflexing at the poll, so fit and mouthpiece matter too.

That points toward a simple routine. Before blaming or changing a bit, look at the basics: do the teeth and mouth need a vet or equine dentist's eyes, does the bit fit the mouth, is the curb strap adjusted as the person who knows your horse prefers? Our bit size page covers measuring, and our gentlest bit page covers why gentle depends on more than the hardware.

If your horse fusses, tosses his head or resists, that is information. A vet or equine dentist can check the mouth, and a trainer can watch you ride. Neither of them will start with a catalog.

We did not read Western association rule books for this page, so we are not stating what they allow. Ask your show office or read the current rules for the class you are entering.

For English classes, the question comes down to the whole bit, including the cheeks and mouthpiece. Our hunter and equitation bit rules page reports what the USEF chapters say for those divisions, and our dressage bit legality page does the same for dressage. Neither lists a Tom Thumb by name, so check your exact bit against the book or ask the steward.

A listing that says a bit is show legal is a seller's description, not a ruling.

A short list helps:

• What is the problem, and could training, a lesson or a check by the vet or equine dentist address it first?
• Which cheek is it: short shanks, longer curved shanks, a pelham or a sliding design? They act differently.
• Curb strap or chain, and who adjusts it? UGA says the setting changes poll pressure.
• What mouthpiece material and thickness? Our mouthpiece material page explains the options.
• Is it the right size? See the bit size page to measure.
• Does my discipline's rule book or my show's prize list allow it?